JP2009233508A - Method for forming layered coating film and coated object - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a layered coating film, in which layer blending properties of the layered coating film between the adjacent coating film layers are controlled to create an original glorious feeling of a metallic coating film or a dense feeling of a lustering pigment when an intermediate coating composition, a base coating composition and a clear coating composition are applied in this order onto a base material by a wet-on-wet coating method to form the layered coating film. <P>SOLUTION: The method for forming the layered coating film includes the steps of: applying the intermediate coating composition, the base coating composition and the clear coating composition in this order; and using a three-coat one-bake process. The base coating composition is a solvent-type base coating composition which comprises (A) a urea-modified acrylic resin, (B) a urethane-modified polyester resin, (C) a melamine resin and (D) the lustering pigment and has 60/40 to 95/5 of the mass ratio of (solid content of (A) the urea-modified acrylic resin)/(solid content of (B) the urethane-modified polyester resin), and the clear coating composition is a two-liquid type clear coating composition. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for coating an object such as an automobile body with an intermediate coating composition, a base coating composition, and a clear coating composition sequentially by wet-on-wet, and a coating film forming method. The present invention relates to an article having a laminated coating film to be obtained.

  Laminated coatings for automobile bodies and the like include a method of baking and curing each time each constituent coating film is formed, and a method of simultaneously curing a plurality of laminated coating films. Among these, the method of simultaneously curing a plurality of laminated coating films has an advantage that the baking and drying step can be omitted. For example, Japanese Patent Application Laid-Open No. 2001-302964 (Patent Document 1) discloses a 3-coat 1-bake method in which an intermediate coating film, a base coating film, and a clear coating film are sequentially formed by wet-on-wet coating. Yes. In the present invention, by including an amide group-containing acrylic resin in the intermediate coating composition, it is possible to control the familiarity and reversal at the interface between the coating layers, and to eliminate the peeling on the electrodeposited coating surface caused by chipping. The method is proposed.

  In JP 2002-153805 A (Patent Document 2), an intermediate coating composition containing an amide group-containing acrylic resin and an amino resin and a blocked isocyanate as a curing agent is used in a 3-coat 1-bake method. Discloses a method for controlling the conformity and reversal at the interface between the respective coating film layers, and further forming a laminated coating film having excellent coating film properties, particularly chipping resistance.

  In the case of forming a laminated coating film by the method of 3 coats and 1 bake, the baking drying oven for intermediate coating can be omitted, and a great effect can be created from the economical and environmental aspects. However, on the other hand, since the amount of heat energy applied to the intermediate coating film is reduced, the physical properties of the coating film are lowered, and when used as a coating film forming method for automobile bodies, it causes a serious defect.

  In JP-A No. 2003-211085 (Patent Document 3), by adding a urethane-modified polyester resin, a melamine resin, a blocked isocyanate compound, a non-aqueous dispersion resin having a core-shell structure, and a flat pigment to the intermediate coating composition, The method of controlling the familiarity and reversal at the interface between each coating layer and reducing the size of the peeling and peeling area on the electrodeposition coating surface caused by chipping has been shown. Is planned.

  Originally, the purpose of painting a metallic base coating composition is to produce an excellent design that makes use of the glitter of the glitter pigment, and in recent years, the metallic coating film is required to have a fine glitter feeling. It has been. However, the invention described in Japanese Patent Application Laid-Open No. 2003-211085 cannot be said to fulfill its purpose sufficiently. Further, from the demand for further improvement in economic efficiency and reduction of environmental burden in the painting process, development of a low-temperature curable coating composition and development of a coating method using the same have been desired.

JP 2001-302964 A JP 2002-153805 A Japanese Patent Laid-Open No. 2003-211085

  The object of the present invention is to laminate a base coating composition and a top coating composition, particularly a top coating composition comprising a base coating composition and a clear coating composition, sequentially on a substrate by wet-on-wetting. When forming a coating film, it is a method that controls the familiarity and reversal at the interface between each coating layer, that is, the intermixing property, and further reduces the number of times the coating film is baked and cured. Another object of the present invention is to provide a method capable of forming a laminated coating film having the original glitter feeling of the metallic coating film and the dense feeling of the glitter pigment. Another object of the present invention is to make it possible to cure a coating film under a lower temperature condition and to promote energy saving.

  It is important to adjust the curing reaction rate in each coating layer as a method of improving the appearance of the laminated coating film obtained by a three-coat one-bake system that cures three layers of multilayer films simultaneously by one baking. . However, since the intermediate coating film and the base coating film generally contain a large amount of pigment, it is difficult to adjust the apparent curing rate. The present invention solves this problem. The present inventors have focused on the clear coating film and found an epoch-making coating method that can solve the above-mentioned problems all at once by using a two-pack type clear coating composition in a three-coat one-bake system.

That is, the present invention
An intermediate coating composition, a base coating composition, and a clear coating composition are sequentially applied on a substrate on which an electrodeposition coating film is formed by wet-on-wet to form a coating film. A method for forming a laminated coating film comprising a step of baking and curing layers simultaneously,
This base coating composition has the following components:
Urea-modified acrylic resin (A) 20-65 mass%;
5 to 40% by mass of a urethane-modified polyester resin (B) obtained by polycondensation of a hydroxyl group-containing polyester resin and a diisocyanate compound and having a weight average molecular weight (Mw) of 2000 to 20000;
Melamine resin (C) 10-40% by mass
(The amount of (A) to (C) is based on the solid content mass of the coating composition resin); and the pigment concentration (PWC) of the glitter pigment (D) (based on the solid content mass of the coating composition) 1-23.0%:
A solvent-based base coating composition comprising:
The solid mass ratio of the urea-modified acrylic resin (A) and the urethane-modified polyester resin (B) is 60/40 to 95/5, and the clear coating composition is a two-pack type clear coating composition. Is,
A method for forming a laminated coating film is provided, whereby the above object is achieved.

The intermediate coating composition has the following components:
A hydroxyl group-containing polyester resin obtained by polycondensation of an acid component containing 80 mol% or more of isophthalic acid and a polyhydric alcohol and having a glass transition point (Tg) of 40 to 80 ° C. is reacted with an aliphatic diisocyanate compound. The urethane-modified polyester resin (i) having a number average molecular weight (Mn) of 1500 to 3000, obtained by 40 to 56% by mass;
Melamine resin (ii) 10-30% by mass;
Blocked isocyanate compound (iii) 15-30% by mass, in which an isocyanate compound obtained by reacting with hexamethylene diisocyanate or hexamethylene diisocyanate and a compound that reacts with it is blocked with a compound having an active methylene group;
Non-aqueous dispersion resin (iv) having a core-shell structure 4 to 15% by mass
(The amount of (i) to (iv) is based on the solid content mass of the coating composition resin); and a flat pigment (v) 0 having a major axis of 1 to 10 μm and a number average particle size of 2 to 6 μm .4 to 2 parts by mass (the coating composition resin solid content is 100 parts by mass);
It is preferable that the coating composition contains an intermediate coating.

  The base coating composition further comprises fatty acid amide (E) 0.1 to 5% by mass; cellulose derivative (F) 0.1 to 10% by mass; and particulate barium sulfate (G) 1 to 20% by mass ( However, the amount of (E) to (F) is based on the resin solid content mass, and the amount of (G) is based on the coating composition solid content mass). It is preferable to contain.

As one aspect of the present invention, the two-component clear coating composition is
An isocyanate compound (X), and a film-forming resin having a hydroxyl group (Y),
And a two-component clear coating composition containing

In another embodiment of the present invention, the two-component clear coating composition is
(A) an acid anhydride group-containing acrylic resin obtained by copolymerizing an acid anhydride group-containing ethylenically unsaturated monomer and an ethylenically unsaturated monomer having no acid anhydride group,
(A) a carboxyl group-containing polyester resin obtained by reacting a polyester polyol having three or more hydroxyl groups with an acid anhydride group-containing compound, and (c) a hydroxyl group-containing ethylenically unsaturated monomer and an epoxy group-containing compound. An acrylic resin having a hydroxyl group and an epoxy group, obtained by copolymerizing an ethylenically unsaturated monomer and an ethylenically unsaturated monomer having neither a hydroxyl group nor an epoxy group,
And a two-component clear coating composition containing

  The present invention further provides a coated product having a multilayer coating film obtained by any one of the above-described multilayer coating film forming methods.

  The laminated coating film obtained by sequentially applying the intermediate coating composition, the base coating composition and the clear coating composition by the method of the present invention by wet-on-wet is excellent in glossiness and is also subject to chipping. In addition, there is an advantage that the peeling area is small in appearance and the peeling frequency is low. Further, the laminated coating film does not cause color reversion due to the mixing of the metallic base coating film and the clear coating film, and does not cause deterioration in appearance or physical properties of the coating film. The laminated coating film obtained according to the present invention is particularly excellent in transparency, can provide a fine glitter feeling such that the glitter pigment is uniformly dispersed, and an FF feeling in which the metallic feeling changes remarkably depending on the viewing angle. It is an excellent coating film.

  In the method for forming a laminated coating film of the present invention, the baking and drying furnace for the intermediate coating material and the base coating material can be omitted. Furthermore, in the formation of a multilayer coating film by a 3-coat 1-bake system, by using a low-temperature curable clear coating composition, it is more economical and the burden on the environment can be further reduced. By the method of the present invention, a laminated coating film can be formed industrially stably.

  In the coating method of the present invention, an intermediate coating composition, a base coating composition, and a clear coating composition are used. Hereinafter, each coating composition will be described.

Intermediate coating composition In the coating film forming method of the present invention, an intermediate coating composition is used for forming the intermediate coating film. This intermediate coating composition contains a urethane-modified polyester resin (i), a melamine resin (ii), a blocked isocyanate compound (iii), a non-aqueous dispersion resin (iv) having a core-shell structure, and a flat pigment (v) To do. The intermediate coating composition may further contain various organic or inorganic color pigments and extender pigments.

Urethane-modified polyester resin (i)
The urethane-modified polyester resin (i) can be obtained by reacting a hydroxyl group-containing polyester resin with an aliphatic diisocyanate compound.

  The polyester resin can generally be produced by polycondensation of an acid component such as a polyvalent carboxylic acid and / or an acid anhydride and a polyhydric alcohol. The hydroxyl group-containing polyester resin used for the preparation of the urethane-modified polyester resin (i) is manufactured using an acid component containing isophthalic acid in the acid component in an amount of 80 mol% or more based on the total number of moles of the acid component. . When the amount of isophthalic acid in the acid component is less than 80 mol%, the glass transition point (Tg) of the resulting hydroxyl group-containing polyester resin is lowered, which is not preferable for use.

  The hydroxyl group-containing polyester resin has a glass transition point (Tg) of 40 to 80 ° C, preferably 45 to 75 ° C. When the glass transition point (Tg) is lower than the lower limit, the coating film hardness is lowered, and when the glass transition point (Tg) is higher than the upper limit, the chipping resistance may be lowered.

  The polyvalent carboxylic acid and / or acid anhydride other than isophthalic acid contained in the acid component used for the preparation of the hydroxyl group-containing polyester resin is not particularly limited. For example, phthalic acid, phthalic anhydride, tetrahydrophthalic acid, tetrahydro Phthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, methyltetrahydrophthalic acid, methyltetrahydrophthalic anhydride, hymic anhydride, trimellitic acid, trimellitic anhydride, pyromellitic acid, pyromellitic anhydride, terephthalic acid, Examples thereof include maleic acid, maleic anhydride, fumaric acid, itaconic acid, adipic acid, azelaic acid, sebacic acid, succinic acid, succinic anhydride, dodecenyl succinic acid, dodecenyl succinic anhydride and the like.

  The polyhydric alcohol used for the preparation of the hydroxyl group-containing polyester resin is not particularly limited. For example, ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, neopentyl glycol, 1,2-butanediol. 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanediol, 2,2-dimethyl-3 -Hydroxypropyl-2,2-dimethyl-3-hydroxypropionate, 2,2,4-trimethyl-1,3-pentanediol, polytetramethylene ether glycol, polycaprolactone polyol, glycerin, sorbitol An'nitoru, trimethylol ethane, trimethylol propane, trimethylol butane, hexanetriol, pentaerythritol, dipentaerythritol and the like.

  In the preparation of the hydroxyl group-containing polyester resin, other reaction components may be used in addition to the polyvalent carboxylic acid and / or acid anhydride and the polyhydric alcohol component. Examples of such other reaction components include monocarboxylic acid, hydroxycarboxylic acid, and lactone. Moreover, you may use drying oil, semi-drying oil, and those fatty acids. Specific examples include monoepoxide compounds such as Cardura E (manufactured by Shell Chemical Co., Ltd.) and lactones. The lactones can be subjected to ring-opening addition to polyesters of polyvalent carboxylic acids and polyhydric alcohols to form graft chains. For example, β-propiolactone, dimethylpropiolactone, butyllactone, γ- Examples include valerolactone, ε-caprolactone, γ-caprolactone, γ-caprolactone, crotolactone, δ-valerolactone, and δ-caprolactone, among which ε-caprolactone is most preferable.

  The urethane-modified polyester resin (i) is prepared by reacting the thus obtained hydroxyl group-containing polyester resin with an aliphatic diisocyanate compound. Specific examples of such aliphatic diisocyanate compounds include hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, dicyclohexylmethane-4,4-diisocyanate, and methylcyclohexane diisocyanate. . Among these, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and their burette, nurate, and adducts are preferably used from the viewpoint of chipping resistance and weather resistance.

  In preparation of the urethane-modified polyester resin (i), it is preferable to react 5 to 15 parts by mass of the aliphatic diisocyanate compound with respect to 100 parts by mass of the hydroxyl group-containing polyester resin. The number average molecular weight of the urethane-modified polyester resin (i) is preferably 1200 to 3000, and more preferably 1500 to 2500. Below the lower limit, the coating workability and curability may be insufficient. On the other hand, when the upper limit is exceeded, the non-volatile content at the time of painting becomes too low, and the workability becomes worse. In the present specification, the number average molecular weight and the weight average molecular weight are determined by a GPC method using a styrene polymer as a standard.

  The urethane-modified polyester resin (i) preferably has a hydroxyl value (solid content) of 30 to 180, more preferably 40 to 160. If the upper limit is exceeded, the water resistance in the case of a coating film may be reduced, and if the lower limit is exceeded, the curability of the coating film may be reduced. Moreover, it is preferable that the acid value of urethane-modified polyester resin (i) is 3-30 mgKOH / g (solid content), More preferably, it is 5-25 mgKOH / g. If it exceeds the upper limit, the water resistance of the coating film may be lowered, and if it is less than the lower limit, the curability of the coating film may be lowered.

  Content of the said urethane-modified polyester resin (i) in the intermediate coating composition of this invention is 40-56 mass% on the basis of coating composition resin solid content mass. If the content of the urethane-modified polyester resin (i) is less than 40% by mass, the chipping resistance in the case of forming a coating film may be insufficient. Moreover, when content exceeds 56 mass%, when it is set as a coating film, there exists a possibility that hardness may fall. The content is preferably 43 to 50% by mass.

Melamine resin (ii)
The melamine resin is not particularly limited, and a methylated melamine resin, a butylated melamine resin, or a methylbutyl mixed melamine resin can be used. For example, “Cymel 303” and “Cymel 254” commercially available from Nippon Cytec Co., Ltd., “Uban 128” and “Uban 20N60” commercially available from Mitsui Chemicals, Inc., and commercially available from Sumitomo Chemical Co., Ltd. “Sumimar series” and the like.

  The said melamine resin (ii) is contained 10-30 mass% on the basis of coating composition resin solid content mass. If the content is less than the lower limit, the curability may be insufficient, and if the content exceeds the upper limit, the cured film may be too hard and brittle. The content of the melamine resin (ii) is preferably 15 to 25% by mass.

Block isocyanate compound (iii)
The blocked isocyanate compound (iii) has an active methylene group in hexamethylene diisocyanate or an isocyanate compound obtained by reacting with hexamethylene diisocyanate and a compound that reacts with it, for example, a multimer such as its nurate. What is obtained by adding a compound is mentioned. In this blocked isocyanate compound (iii), the blocking agent is dissociated by heating to generate an isocyanate group, which reacts with the functional group in the urethane-modified polyester resin and cures. Examples of the compound having an active methylene group include active methylene compounds such as acetylacetone, ethyl acetoacetate, and ethyl malonate.

  Content of the said block isocyanate compound is 15-30 mass% on the basis of coating composition resin solid content mass. More preferably, it is 17-25 mass%. Outside the above range, curing may be insufficient. Specific examples include active methylene type blocked isocyanate “Duranate MF-K60X” manufactured by Asahi Kasei Corporation.

Non-aqueous dispersion resin (iv)
The non-aqueous dispersion resin (iv) having the above core-shell structure is prepared as resin particles insoluble in this mixed solution by copolymerizing a polymerizable monomer in a mixed solution of a dispersion stable resin and an organic solvent. can do. The “non-aqueous dispersion” means a non-aqueous dispersion type resin, and is obtained by dispersing and stabilizing a resin using an organic solvent as a medium.

  The resin particles in the non-aqueous dispersion resin (iv) are preferably prepared as non-crosslinked resin particles. The monomer to be copolymerized in the presence of the dispersion-stable resin for obtaining non-crosslinked resin particles is not particularly limited as long as it is a radical polymerizable unsaturated monomer.

  However, it is preferable to use a polymerizable monomer having a functional group in the synthesis of the dispersion stabilizing resin and the non-aqueous dispersion resin (iv). This is because the non-aqueous dispersion resin (iv) having a functional group can react with a post-curing agent together with a dispersion-stabilizing resin containing a functional group to form a three-dimensionally crosslinked coating film.

  The dispersion stable resin is not particularly limited as long as it can stably synthesize the non-aqueous dispersion resin (iv) in an organic solvent. Specifically, as the dispersion stable resin, the hydroxyl value (solid content) is 10 to 250, preferably 20 to 180, and the acid value (solid content) is 0 to 100 mgKOH / g, preferably 0 to 50 mgKOH / g, It is preferable to use an acrylic resin, a polyester resin, a polyether resin, a polycarbonate resin or a polyurethane resin having a number average molecular weight of 800 to 100,000, preferably 1000 to 20,000. If these upper limits are exceeded, the handling properties of the resin may be reduced, and the handling of the non-aqueous dispersion itself may also be reduced. If the lower limit is not reached, the resin may be detached or the stability of the particles may be reduced when the coating film is formed.

  The method for synthesizing the dispersion stable resin is not particularly limited, and preferred examples include a method obtained by radical polymerization in the presence of a radical polymerization initiator, a method obtained by a condensation reaction or an addition reaction, and the like. Furthermore, the monomer used to obtain the dispersion-stable resin can be appropriately selected according to the properties of the resin, but has a polymerizable monomer used to synthesize a non-aqueous dispersion described later. It is preferable to use those having a functional group such as a hydroxyl group and an acid group, and if necessary, those having a functional group such as a glycidyl group and an isocyanate group may be used.

  The non-aqueous dispersion resin (iv) can be obtained by polymerizing a polymerizable monomer in a mixed liquid of a dispersion stable resin and an organic solvent. As the polymerizable monomer, a radical polymerizable monomer can be used. This organic solvent dissolves the dispersion stable resin but does not dissolve the resin particles obtained by polymerizing the polymerizable monomer, and can be appropriately selected from various organic solvents.

  As the polymerizable monomer used for the synthesis of the non-aqueous dispersion resin (iv), a monomer having a functional group is preferably used. Typical examples of the polymerizable monomer having a functional group are as follows. Examples of the polymerizable monomer having a hydroxyl group include hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, hydroxymethyl methacrylate, allyl alcohol, and hydroxy (meth) methacrylate. Examples include adducts of ethyl and ε-caprolactone.

  On the other hand, examples of the polymerizable monomer having an acid group include polymerizable monomers having a carboxyl group, a sulfonic acid group, and the like. Examples of those having a carboxyl group include (meth) acrylic acid, crotonic acid, ethacrylic acid, propylacrylic acid, isopropylacrylic acid, itaconic acid, maleic anhydride, fumaric acid and the like. Examples of the polymerizable monomer having a sulfonic acid group include t-butylacrylamide sulfonic acid. When using the polymerizable monomer which has an acid group, it is preferable that a part of acid group is a carboxyl group.

  In addition, glycidyl group-containing unsaturated monomers such as glycidyl (meth) acrylate, isocyanate group-containing unsaturated monomers such as m-isopropenyl-α, α-dimethylbenzyl isocyanate, isocyanatoethyl acrylate, etc. Is mentioned as a polymerizable monomer having a functional group.

  Other polymerizable monomers include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-propyl (meth) acrylate, and n- (meth) acrylate. Butyl, t-butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, (Meth) acrylic acid alkyl ester such as tridecyl methacrylate, addition reaction product of oil fatty acid and acrylic acid or methacrylic acid ester monomer having oxirane structure (for example, addition reaction product of stearic acid and glycidyl methacrylate), carbon number 3 Oxirane compounds containing the above alkyl groups and acrylic acid or methacrylic acid Addition reaction product of styrene, α-methyl styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, pt-butyl styrene, benzyl (meth) acrylate, itaconic acid ester (dimethyl itaconate, etc.) , Maleic acid esters (such as dimethyl maleate), fumaric acid esters (such as dimethyl fumarate), acrylonitrile, methacrylonitrile, methyl isopropenyl ketone, vinyl acetate, Veova monomer (made by Shell Chemical Co., Ltd., trade name), vinyl Examples thereof include polymerizable monomers such as propionate, vinyl pivalate, ethylene, propylene, butadiene, N, N-dimethylaminoethyl acrylate, N, N-dimethylaminoethyl methacrylate, acrylamide, and vinyl pyridine.

  In the preparation of the non-aqueous dispersion resin (iv), the composition ratio of the dispersion stable resin and the polymerizable monomer can be arbitrarily selected according to the purpose. For example, the dispersion stable resin is based on the total mass of the two components. Is preferably 3 to 80% by mass, particularly 5 to 60% by mass, and the polymerizable monomer is preferably 97 to 20% by mass, and particularly preferably 95 to 40% by mass. Furthermore, the total concentration of the dispersion stable resin and the polymerizable monomer in the organic solvent is preferably 30 to 80% by mass, particularly preferably 40 to 60% by mass, based on the total mass.

  The polymerization reaction for obtaining the non-aqueous dispersion is preferably performed in the presence of a radical polymerization initiator. Examples of the radical polymerization initiator include azo initiators such as 2,2′-azobisisobutyronitrile and 2,2′-azobis (2,4-dimethylvaleronitrile), benzoyl peroxide, lauryl peroxide, Examples include t-butyl peroctoate. These initiators are used in an amount of 0.2 to 10 parts by mass, preferably 0.5 to 5 parts by mass per 100 parts by mass of the polymerizable monomers. In general, the polymerization reaction for obtaining a non-aqueous dispersion in an organic solvent containing a dispersion-stable resin is preferably performed in a temperature range of about 60 to 160 ° C. for about 1 to 15 hours.

The non-aqueous dispersion resin (iv) thus obtained has a hydroxyl value (solid content) of 50 to 400, preferably 100 to 300, and an acid value (solid content) of 0 to 200 mgKOH / g, preferably 0 to 50 mgKOH. / g, an average particle diameter _{(D 50)} 0.05 to 10 [mu] m, it is preferable preferably 0.1-2 .mu.m. If the lower limit is not reached, the particle shape may not be maintained, and if the upper limit is exceeded, the stability when dispersed in the coating composition may be reduced. The average particle diameter (D ₅₀ ) can be measured by a dynamic light scattering method. Specifically, it can be measured using a nanotrack particle size distribution measuring apparatus UPA (manufactured by Nikkiso Co., Ltd.).

  Further, the non-aqueous dispersion is different from the crosslinked polymer fine particles, and is a particle component in the coating composition, but has a characteristic that a particle structure is not formed in the coating film. That is, the non-aqueous dispersion is different from the crosslinked polymer fine particles in that there are no cross-linked sites in the particles, so that the particle shape changes during the baking process and can become a resin component.

  Furthermore, for example, resin particles called NAD (Non Aqueous Dispersion) used in the NAD coating composition described in Color Material, Vol. 48 (1975), pages 28 to 34, are also used. Can be used.

  Content of non-aqueous dispersion resin (iv) in the intermediate coating composition of this invention is 4-15 mass% on the basis of coating composition resin solid content mass. If the content is below the lower limit, the overall coating film appearance may be insufficient, and if it exceeds the upper limit, the chipping resistance may be reduced. This content is preferably 5 to 12% by mass.

Flat pigment (v)
The flat pigment (v) is a pigment in which at least one surface of the pigment has a flat shape. Examples of the flat pigment (v) include mica, alumina, talc and silica. Of these, talc is preferably used. This is because the chipping performance of the coating film can be improved.

  The flat pigment preferably has a major axis of 1 to 10 μm and a number average particle diameter of 2 to 6 μm. Here, the major axis is the length of the diameter in the flat plane of the flat pigment. The number average particle diameter is an average particle diameter obtained by selecting a predetermined number of particles from a scanning electron micrograph and performing image analysis to obtain an average value of the equivalent circle diameter and its distribution. Here, the equivalent circle diameter refers to the value of the diameter when the pigment is converted into the diameter of a perfect circle having the same area. These diameters and number average particle diameters can be measured by using a scanning electron microscope or the like. When the long diameter of the flat pigment is outside the above range, the appearance of the coating film may be inferior or it may be difficult to develop sufficient chipping resistance. Further, when the number average particle size is outside the above range, the appearance of the coating film is similarly inferior, and it may be difficult to develop sufficient chipping resistance.

  The content of the flat pigment (v) is 0.4 to 2 parts by mass based on 100 parts by mass of the resin solid content in the coating composition. This content is more preferably 0.5 to 1.5 parts by mass. Outside the above range, the adhesion with the base coating film may be lowered, and there is a risk that sufficient chipping performance may not be obtained.

The other component intermediate coating composition may further contain other components in addition to the components (i) to (v). Examples of other components include a resin component. The resin component that can be used is not particularly limited, and examples thereof include acrylic resins, polyester resins, alkyd resins, and epoxy resins. These may use only 1 type and may use 2 or more types together. However, it is not preferable to include a resin having an epoxy group that hinders storage stability.

  As other components, a color pigment or the like can also be used. Color pigments include organic azo chelate pigments, insoluble azo pigments, condensed azo pigments, diketopyrrolopyrrole pigments, benzimidazolone pigments, phthalocyanine pigments, indigo pigments, perinone pigments, perylene pigments, Examples include dioxane pigments, quinacridone pigments, isoindolinone pigments, metal complex pigments, and inorganic pigments such as yellow lead, yellow iron oxide, bengara, carbon black, and titanium dioxide. Furthermore, calcium carbonate, barium sulfate, aluminum powder, kaolin and the like can be used as extender pigments.

  In general, for the intermediate coating composition, a gray-based one containing carbon black and titanium dioxide as main pigments is used. In addition, a combination of hues with the top coat and a combination of various color pigments can be used.

  Furthermore, a viscosity control agent can be added to the intermediate coating composition. As a result, it is possible to prevent familiarity with the top coat film and to ensure coating workability. Viscosity control agents can generally include those exhibiting thixotropic properties, such as swelling dispersions of fatty acid amides, polyamides such as amide fatty acids, phosphates of long-chain polyaminoamides, colloidal swelling dispersion of oxidized polyethylene Such as polyethylene-based bodies, organic acid smectite clay, organic bentonite-based materials such as montmorillonite, inorganic pigments such as aluminum silicate and barium sulfate, flat pigments that develop viscosity depending on the shape of the pigment, crosslinked resin particles, etc. It can be mentioned as a viscosity control agent.

  The total solid content during coating of the intermediate coating composition used in the present invention is 30 to 80% by mass, preferably 35 to 65% by mass. Outside this range, the coating composition stability may be reduced. On the other hand, when the upper limit is exceeded, the viscosity is too high and the appearance of the coating film is lowered, and when below the lower limit, the viscosity is too low and appearance defects such as familiarity and unevenness may occur. In the intermediate coating composition used in the present invention, additives usually added to the coating composition, for example, a surface conditioner, an antioxidant, an antifoaming agent, etc. may be blended in addition to the above components. . These compounding amounts are within the range known to those skilled in the art.

  The method for producing the coating composition used in the present invention is not particularly limited, including those described later, and those skilled in the art such as kneading and dispersing a compound such as a pigment using a kneader or roll, a sand grinder mill, etc. Any of the known methods can be used.

Base coating composition The base coating composition used in the present invention is:
Urea-modified acrylic resin (A) 20-65 mass%,
5 to 40% by mass of a urethane-modified polyester resin (B) obtained by polycondensation of a hydroxyl group-containing polyester resin and a diisocyanate compound and having a weight average molecular weight (Mw) of 2000 to 20000,
Melamine resin (C) 10-40% by mass
(The amount of (A) to (C) is based on the solid content mass of the coating composition resin) and
The pigment concentration (PWC) of the glitter pigment (D) (based on the solid content mass of the coating composition) is 1 to 23.0%,
Containing. And the solid content mass ratio of the said urea modified acrylic resin (A) and the said urethane modified polyester resin (B) is 60 / 40-95 / 5.

  The base coating composition preferably further contains one or more components selected from the group consisting of fatty acid amide (E), cellulose derivative (F), and particulate barium sulfate (G).

Urea-modified acrylic resin (A)
As said urea modified acrylic resin (A), the acrylic resin which has a urea bond group (urea group) -NH-CO-NH- can be mentioned. The urea group-NH-CO-NH- is based on the solid content of the urea-modified acrylic resin (A), and the amount of urea group introduction (modification) component when using, for example, the components described later is 1 to 15% by mass. It is preferable that it is 2 to 12% by mass. If it exceeds the upper limit, the appearance (skin feel) may be reduced when it is used as a coating film, and if it is lower than the lower limit, flip-flop properties (difference between lightness in highlight and shade, FF property) and glitter There is a risk that the fineness of the facial material may be reduced. Especially preferably, it is 3-10 mass%. The preparation component and / or method of the urea-modified acrylic resin (A) is not particularly limited. It is important as an effect obtained after coating film preparation to use the acrylic resin which introduce | transduced the urea group in the coating composition of this invention.

  For example, the urea-modified acrylic resin (A) can be synthesized from a reaction between (1) an isocyanate compound, (2) a hydroxyl group-containing acrylic resin, and (3) an amine compound. In this case, the urea group-introducing component is (1) an isocyanate compound and (3) an amine compound.

  Examples of the isocyanate compound (1) include alicyclic, aromatic group-containing aliphatic or aromatic compounds. Examples of suitable isocyanate compounds include diisocyanate or its isocyanurate (triisocyanate of diisocyanate).

  As said diisocyanate, what contains generally 5-24, preferably 6-18 carbon atoms can be used.

  For example, trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexane diisocyanate, undecane diisocyanate- (1,11), lysine ester diisocyanate, cyclohexane-1,3- and 1,4-diisocyanate 1-isocyanato-3-isocyanatomethyl-3,5,5-trimethylcyclohexane (IPDI), 4,4′-diisocyanatodicyclodicyclomethane, ω, ω′-dipropyl ether diisocyanate, thiodipropyl diisocyanate , Cyclohexyl-1,4-diisocyanate, dicyclohexylmethane-4,4′-diisocyanate, 1,5-dimethyl-2,4-bis (isocyanatomethyl) benzene, 1,5-trimethyl Til-2,4-bis (ω-isocyanatoethyl) -benzene, 1,3,5-trimethyl-2,4-bis (isocyanatomethyl) benzene, 1,3,5-triethyl-2,4-bis (Isocyanatomethyl) benzene, dicyclohexyldimethylmethane-4,4′-diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, diphenylmethane-4,4′-diisocyanate and the like.

  2,4-diisocyanatotoluene and / or 2,6-diisocyanatotoluene, 4,4′-diisocyanatodiphenylmethane and 1,4-diisocyanatoisopropylbenzene, cyclohexyl-1,4-diisocyanate, Aromatic diisocyanates such as toluene diisocyanate and hexamethylene diisocyanate can also be used. Furthermore, mixtures of these compounds can also be used.

  As said isocyanurate, the trimer of the diisocyanate mentioned above can be mentioned. The isocyanate may be a diisocyanate or a mixture of trimers.

  The hydroxyl group-containing acrylic resin (2) is a resin obtained by copolymerizing a hydroxyl group-containing ethylenically unsaturated monomer and another ethylenically unsaturated monomer. The hydroxyl group-containing acrylic resin (2) preferably has a number average molecular weight (Mn) of 1000 to 8000, more preferably 1200 to 6000. If the lower limit is not reached, the coating workability and the interlaminarity with the clear coating film may be lowered. If the upper limit is exceeded, the non-volatile content at the time of coating may be lowered, and the workability may be deteriorated. The number average molecular weight of the hydroxyl group-containing acrylic resin (2) is particularly preferably in the range of 1500 to 5000 from the viewpoint of coating film appearance.

  The hydroxyl group-containing acrylic resin (2) preferably has a hydroxyl value (solid content) of 40 to 180, and more preferably 50 to 150. If the upper limit is exceeded, the water resistance may decrease when the coating film is formed, and if the lower limit is exceeded, the curability of the coating film may decrease. Furthermore, it preferably has an acid value (solid content) of 7 to 32 mgKOH / g, and more preferably 10 to 27 mgKOH / g. If the upper limit is exceeded, the water resistance may decrease when the coating film is formed, and if the lower limit is exceeded, the curability of the coating film may decrease.

  The hydroxyl group-containing acrylic resin (2) can be obtained by copolymerizing a hydroxyl group-containing ethylenically unsaturated monomer and another ethylenically unsaturated monomer. The blending ratio in this copolymerization is 5 to 60% by mass, preferably 8 to 50% by mass of the hydroxyl group-containing ethylenically unsaturated monomer, based on the total amount of the ethylenically unsaturated monomer used to produce the acrylic resin. The other ethylenically unsaturated monomer is 95 to 40% by mass, preferably 92 to 50% by mass. If the content of the hydroxyl group-containing ethylenically unsaturated monomer is below the lower limit, production stability may be reduced. If it exceeds the upper limit, the water resistance in the case of a coating film obtained may be lowered.

  Specific examples of the hydroxyl group-containing ethylenically unsaturated monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, allyl alcohol, and methacryl alcohol. Examples include adducts of hydroxyethyl (meth) acrylate and ε-caprolactone. Among these, it is preferable to use a long-chain hydroxyl group-containing monomer as the hydroxyl group-containing monomer in terms of improving chipping resistance. Examples thereof include 4-hydroxybutyl (meth) acrylate, adducts of 2-hydroxyethyl (meth) acrylate and ε-caprolactone.

  Although it does not specifically limit as said other ethylenically unsaturated monomer, For example, the ethylenically unsaturated monomer which has a carboxyl group can be mentioned. Examples thereof include (meth) acrylic acid derivatives (e.g., acrylic acid, methacrylic acid, crotonic acid, isocrotonic acid, acrylic acid dimer, and α-hydro-ω-((1 -Oxo-2-propenyl) oxy) poly (oxy (1-oxo-1,6-hexanediyl)) etc.); and unsaturated dibasic acids, their half esters, half amides and half thioesters (eg maleic acid, Fumaric acid, itaconic acid, its half ester, half amide, half thioester, etc.).

  Furthermore, examples other than the above monomers include (meth) acrylate ester monomers (for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) ) Acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, phenyl (meth) acrylate, isobornyl (meth) acrylate, cyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, dicyclopentadienyl ( Meth) acrylate and dihydrodicyclopentadienyl (meth) acrylate), polymerizable aromatic compounds (eg styrene, α-methyl styrene, vinyl ketone, t-butyl styrene, parachlorostyrene and Vinyl naphthalene etc.), polymerizable nitriles (eg acrylonitrile and methacrylonitrile etc.), α-olefins (eg ethylene and propylene etc.), vinyl esters (eg vinyl acetate and vinyl propionate etc.), dienes (eg butadiene and isoprene etc.) If necessary, an isocyanate group-containing monomer can be mentioned. Such other ethylenically unsaturated monomers can be used alone or in admixture of two or more.

  A hydroxyl group-containing acrylic resin can be obtained by radical copolymerization of each of the above ethylenically unsaturated monomers. As the polymerization method, a usual method described in known literature such as solution radical polymerization can be used. For example, a method of stirring while dropping a suitable radical polymerization initiator and a monomer mixed solution into a suitable solvent at a polymerization temperature of 60 to 160 ° C. over 2 to 10 hours can be mentioned. The radical polymerization initiator that can be used here is not particularly limited as long as it is usually used in polymerization, and examples thereof include azo compounds and peroxides. Generally, the amount of initiator relative to the total amount of ethylenically unsaturated monomer is generally 0.1 to 18% by weight, preferably 0.5 to 15% by weight.

  Moreover, the solvent which can be used here will not be specifically limited if it does not have a bad influence on reaction, For example, alcohol, a ketone, a hydrocarbon type solvent, etc. are mentioned. Furthermore, the molecular weight can be adjusted by using a mercaptan such as lauryl mercaptan and a chain transfer agent such as α-methylstyrene dimer, if necessary.

  As a typical example of the amine compound (3), which is the third component used in the production of the urea-modified acrylic resin (A), generally 55 or less carbon atoms, preferably 1 to 24, more preferably 1 And ether amines and primary amines containing ˜12 carbon atoms.

  The ether amine may contain one or more hydroxyl groups, such as 2-methoxyethylamine, 2-ethoxyethylamine, 3-methoxy-1-propylamine, 1-methoxymethylpropylamine, 1,1 -Dimethoxy-2-propylamine, 3-ethoxy-1-propylamine, 3-butoxy-1-propylamine, 3- (2-ethylhexyloxy) -1-propylamine, 3-tridecyloxypropylamine, 3- Stearyloxypropylamine, p-methoxybenzylamine, 3,4-dimethoxybenzylamine, p-methoxyphenylethylamine, 3,4-dimethoxyphenyl-ethylamine, 9-phenoxy-4,7-dioxanon-1-amine, 2- Methyl-4-methoxyaniline, 2,5-di Toxi-aniline, furfurylamine, tetrahydrofurfurylamine, 2- (4-morpholinyl) ethylamine, 4- (3-aminopropyl) morpholine, 2,2'-aminoethoxyethanol, 4,7-dioxadecane-1,10-diamine 4,9-dioxadecane-1,12-diamine, 7-methyl-4,10-dioxatridecane-1,13-diamine, 4,7,10-trioxatridecane-1,13-diamine and bis (3-aminopropyl) polytetrahydrofuran (molecular weight about 750). A mixture of the above ether amines can also be used.

  Further, as the primary amine, an amine having one or more primary amino groups and one or more ethers and / or hydroxyl groups can be used, for example, ethanolamine, 6-aminohexanol, p-methoxybenzylamine. , Methoxypropylamine, 3,4-dimethoxyphenylethylamine, 2,5-dimethoxyaniline, furfurylamine, tetrahydrofurfurylamine, benzylamine, ethylamine, n-propylamine, sec-propylamine, n-butylamine, sec-butylamine, tert-butylamine, n-pentylamine, α-methylbutylamine, α-ethylpropylamine, β-ethylbutylamine, hexylamine, octylamine, decylamine, stearylamine, cyclohexylamino , Aniline, primary amines such as hexamethylene diamine and the like. The above amine compounds can be mixed and used.

As a detailed preparation method of the urea-modified acrylic resin (A), for example, the following method may be mentioned;
-After reacting the isocyanate compound (1) and the previously synthesized hydroxyl group-containing acrylic resin (2) so that the isocyanate group of the compound (1) is excessive with respect to the hydroxyl group equivalent of the acrylic resin, unreacted A method of reacting an amine group (3) with an isocyanate group;
-After reacting the isocyanate compound (1) and the amine compound (3) so that the isocyanate group of the isocyanate compound (1) is excessive with respect to the amine equivalent of the amine compound (3), unreacted isocyanate A method of reacting a hydroxyl group-containing acrylic resin (2) with a group;
A method of introduction by copolymerization of an acrylic monomer with a urea functional vinyl monomer, such as an alkyl ester of urea functional acrylic acid or methacrylic acid;
-A method of reacting an amine compound with an acrylic resin synthesized using an isocyanate group-containing monomer.

  The urea-modified acrylic resin (A) is produced by reacting the isocyanate compound (1) and the amine compound (3) in the presence of other binders, curing agents and / or binders or curing agents used in the coating composition. It can also be performed by a method. This method is preferable from the viewpoint of the compatibility of the components in the coating composition system.

  Further, the urea-modified acrylic resin (A) from the above component examples (1) to (3) is produced by the equivalent of the isocyanate group present in the starting component to the isocyanate group present in the starting component. Using the reactants in such a ratio that the ratio (isocyanate reactive groups / isocyanate groups) is 0.5-2, preferably 0.7-1.5, more preferably 0.8-1.2, This is accomplished in a known manner in one or more stages. In particular, in the reaction of the isocyanate compound (1) and the amine compound (3), it is generally possible to use either the isocyanate compound (1) or the amine compound (3) in excess of the stoichiometric amount. it can.

  The reaction between the diisocyanate and the amine compound can be carried out by any method selected by generally mixing these reaction components and raising the temperature as desired. This reaction is desirably performed at a temperature of 10 to 150 ° C, preferably 20 to 80 ° C. In general, the reaction components can be mixed by an arbitrarily selected method, but it is usually desirable to add diisocyanate to the amine compound, and this addition can be carried out in several steps as desired. In general, this reaction is carried out in the presence of a solvent such as an aliphatic hydrocarbon such as acetone, methyl isobutyl ketone, 1-methoxy-2-propanol, benzene, toluene, xylene or petroleum ether.

  The urea group contained in the urea-modified acrylic resin (A) can form a pseudo network structure due to hydrogen bonding in the coating composition, and can exhibit thixotropic properties in the coating composition. And after forming a coating film, it can incorporate in resin at the time of baking, and is suitable. The thixotropy expressed by the urea group in the coating composition is very excellent because it is not affected at all or hardly by the water and / or the organic solvent contained in the coating composition. Further, the thixotropic property expressed by the urea group is hardly affected by temperature, and the viscosity drop does not occur even at a temperature of 60 ° C. to 260 ° C., that is, a temperature at which the baking-type coating composition is generally cured. Small and extremely effective thixotropy can be maintained.

  The urea-modified acrylic resin (A) preferably has a weight average molecular weight (Mw) of 3000 to 150,000, more preferably 4000 to 130,000. If the lower limit is not reached, the coating workability and the interlaminarity with the clear coating film may be lowered. If the upper limit is exceeded, the non-volatile content at the time of coating may be lowered, and the workability may be deteriorated. A range of 5,000 to 120,000 is particularly preferred from the viewpoint of coating film appearance.

  The urea-modified acrylic resin (A) preferably has a hydroxyl value (solid content) of 30 to 180, and more preferably 50 to 150. If the upper limit is exceeded, the water resistance may decrease when the coating film is formed, and if the lower limit is exceeded, the curability of the coating film may decrease. Furthermore, the urea-modified acrylic resin (A) preferably has an acid value (solid content) of 5 to 30 mgKOH / g, and more preferably 8 to 25 mgKOH / g. If the upper limit is exceeded, the water resistance may decrease when the coating film is formed, and if the lower limit is exceeded, the curability of the coating film may decrease.

  Furthermore, the urea-modified acrylic resin (A) preferably has a glass transition temperature (Tg) of −10 to 30 ° C., more preferably 0 to 25 ° C. If it is out of the above range, the physical properties of the coating film may be lowered.

  Content of the said urea modified acrylic resin (A) is 20-65 mass with respect to solid content of film forming resin, such as a urea modified acrylic resin (A), a urethane modified polyester resin (B), and a melamine resin (C). %. If the content is lower than the lower limit, the FF property may be reduced, and if the content exceeds the upper limit, the appearance may be reduced. Preferably it is 25-60 mass%.

Urethane-modified polyester resin (B)
The urethane-modified polyester resin (B) is not particularly limited, and may be the same as or different from the urethane-modified polyester resin (i) contained in the intermediate coating composition. Also good. As the urethane-modified polyester resin (B), for example, a hydroxyl group-containing polyester resin containing a mixture of an acid component such as a polyvalent carboxylic acid and / or an acid anhydride and a polyhydric alcohol, and a diisocyanate compound are used in an excess of hydroxyl groups. The polyester resin obtained by making it react by the ratio of these is mentioned. This urethane-modified polyester resin (B) preferably has two or more hydroxyl groups in one molecule.

  The polyvalent carboxylic acid and / or acid anhydride that can be used for the urethane-modified polyester resin (B) is not particularly limited, and examples thereof include phthalic acid, isophthalic acid, phthalic anhydride, tetrahydrophthalic acid, tetrahydrophthalic anhydride, Hexahydrophthalic acid, hexahydrophthalic anhydride, methyltetrahydrophthalic acid, methyltetrahydrophthalic anhydride, hymic anhydride, trimellitic acid, trimellitic anhydride, pyromellitic acid, pyromellitic anhydride, terephthalic acid, maleic acid anhydride Examples thereof include maleic acid, fumaric acid, itaconic acid, adipic acid, azelaic acid, sebacic acid, succinic acid, succinic anhydride, dodecenyl succinic acid, dodecenyl succinic anhydride and the like.

  Moreover, it does not specifically limit as polyhydric alcohol which can be used for urethane-modified polyester resin (B), For example, it describes with the specific example of the synthetic | combination component of urethane-modified polyester resin quoted by description of the said intermediate coating composition. Can be mentioned.

  The reaction component other than the polyvalent carboxylic acid and / or acid anhydride and the polyhydric alcohol component is not particularly limited. For example, the synthetic component of the urethane-modified polyester resin mentioned in the description of the intermediate coating composition. The components described in the specific examples can be mentioned.

  The diisocyanate compound to be reacted with the hydroxyl group-containing polyester resin is a compound having two or more free isocyanate groups in one molecule, and specifically, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate and trimethylene diisocyanate. Aliphatic diisocyanates such as: isophorone diisocyanate, alicyclic diisocyanates such as methylenebis (cyclohexyl isocyanate) and cyclohexane diisocyanate; aromatic diisocyanates such as xylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate and biphenylene diisocyanate; These can be used alone or in combination of two or more.

  Particularly preferred diisocyanate compounds are aliphatic diisocyanates, specifically hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, dicyclohexylmethane-4,4-diisocyanate, methylcyclohexane diisocyanate and the like. Can be mentioned.

  The reaction conditions of the usual urethanization reaction can be widely applied to the reaction between the hydroxyl group-containing polyester resin and the diisocyanate compound.

  The urethane-modified polyester resin (B) preferably has a weight average molecular weight (Mw) of 2000 to 20000, more preferably 3000 to 15000. Below the lower limit, there is a risk that the coating workability and interlaminarity when applied with wet-on-wet may decrease, and when the upper limit is exceeded, the non-volatile content of the coating composition at the time of coating is reduced, and the coating workability may be reduced. is there.

  The urethane-modified polyester resin (B) preferably has a hydroxyl value (solid content) of 30 to 180, and more preferably 40 to 160. If the upper limit is exceeded, the water resistance in the case of a coating film may be reduced, and if the lower limit is exceeded, the curability of the coating film may be reduced. Moreover, it is preferable that it has an acid value (solid content) of 2-20 mgKOH / g, and it is still more preferable that it is 3-15 mgKOH / g. If the upper limit is exceeded, the water resistance in the case of a coating film may be reduced, and if the lower limit is exceeded, the curability of the coating film may be reduced.

  Furthermore, the urethane-modified polyester resin (B) preferably has a glass transition temperature (Tg) of −10 to 70 ° C., more preferably −5 to 50 ° C. When the glass transition point (Tg) is lower than the lower limit, the coating film hardness may be reduced, and when the glass transition point (Tg) is higher than the upper limit, the solid content of the coating composition may be reduced and the coating workability may be reduced. In general, a polyester resin can be produced by polycondensation of an acid component such as a polyvalent carboxylic acid and / or an acid anhydride and a polyhydric alcohol.

  The content of the urethane-modified polyester resin (B) in the base coating composition is based on the solid content of the film-forming resin such as urea-modified acrylic resin (A), urethane-modified polyester resin (B), and melamine resin (C). 5 to 40% by mass. If the content is less than the lower limit, the interlaminarity may be lowered, and if the content exceeds the upper limit, the FF property may be lowered. A preferable content is 8 to 25% by mass.

  The solid content mass ratio between the urea-modified acrylic resin (A) and the urethane-modified polyester resin (B) is 60/40 to 95/5, more preferably 65/35 to 92/8, and particularly preferably 70. / 30 to 90/10. When the content of the urethane-modified polyester resin (B) is not within the above range, the mixing property at the interface between the base coating and the clear coating may be lowered. Further, due to the deterioration of the interlaminarity at this interface, there is a possibility that color reversion may occur when the clear coating film is formed.

Melamine resin (C)
The melamine resin (C) is not particularly limited, and may be the same as or different from the melamine resin (ii) contained in the intermediate coating composition. As the melamine resin (C), for example, a methylated melamine resin, a butylated melamine resin, or a methyl / butyl mixed melamine resin can be used. Examples include “Cymel-303” and “Cymel 254” manufactured by Nippon Cytec Co., Ltd., “Uban 20N60” and “Uban 128” manufactured by Mitsui Chemicals, and “Summar Series” manufactured by Sumitomo Chemical Co., Ltd.

  The amount of the melamine resin (C) used is 10 to 40% by mass with respect to the solid content of the film-forming resin such as urea-modified acrylic resin (A), urethane-modified polyester resin (B) and melamine resin (C). It is preferable to do. More preferably, it is 15-35 mass%. If the amount used is less than the lower limit, curability may be insufficient. On the other hand, if the upper limit is exceeded, the cured film becomes stiff and the chipping property may be lowered when it is formed into a coating film.

Bright pigment (D)
The shape of the glitter pigment (D) is not particularly limited, and may be further colored. As the luster pigment (D), for example, a scaly pigment having an average particle diameter (D ₅₀ ) of 2 to ₅₀ μm and a thickness of 0.1 to 5 μm is preferable. Those having an average particle diameter in the range of 10 to 35 μm are excellent in glitter and are more preferably used.

  The pigment concentration (PWC) in the coating composition of the glitter pigment (D) is 1 to 23.0%. When the upper limit is exceeded, the appearance of the coating film is lowered. Preferably, it is 1.5% to 20.0%, and more preferably 2.0% to 18.0%. The pigment concentration (PWC) indicates the pigment content (%) based on the resin solid content mass.

  Examples of the glitter pigment (D) include non-colored or colored metallic glitter materials such as metals or alloys and mixtures thereof, interference mica powder, colored mica powder, white mica powder, graphite, colorless or colored flat pigments, and the like. Can be mentioned. Excellent dispersibility and high transparency can be formed, so there are no colored or colored metallic glitter materials such as metals or alloys and their mixtures, interference mica powder, colored mica powder, and white mica powder. preferable. Specific examples of the metal include aluminum, aluminum oxide, copper, zinc, iron, nickel, tin and the like.

  Furthermore, a coloring pigment can be contained if necessary. Examples of the color pigment include the color pigments and inorganic pigments mentioned in the description of the intermediate coating composition. Furthermore, calcium carbonate, barium sulfate, clay, talc and the like may be used in combination as extender pigments.

  The total pigment concentration (PWC) in the metallic paint composition including the glitter pigment (D) and all other pigments is 1 to 50%, preferably 1.5 to 40%. More preferably, it is 2.0% to 30%. If the upper limit is exceeded, the coating film appearance may be reduced.

  The base coating composition used in the present invention may further contain one or more components selected from the group consisting of fatty acid amide (E), cellulose derivative (F) and particulate barium sulfate (G). These components are described below.

Fatty acid amide (E)
The fatty acid amide (E) used in the base coating composition used in the present invention is generally known as a viscosity control agent for imparting thixotropy. By adding such fatty acid amide (E) to the base coating composition, it is possible to prevent sedimentation of scaly glittering pigments such as aluminum flakes that easily settle during storage.

  An example of the fatty acid amide (E) is diamide having a general structure as shown in the following formula (1).

The diamide is a compound obtained by reacting a diamine with a hydroxyl group-containing fatty acid. In the above formula (1), R ¹ represents a residue obtained by removing a hydroxyl group and a carboxyl group from a hydroxyl group-containing fatty acid, and R ² represents a residue obtained by removing an amino group from a diamine. In the above diamides, fatty acid amides in which no OH group is bonded to either one of R ¹ at both ends are also known as viscosity control agents and can be used in the present invention.

  Moreover, the polyamide which has a general structure shown to following formula (2) as another example of a fatty acid amide is mentioned.

Said polyamide is a compound obtained by making polybasic carboxylic acid, diamine, and a hydroxyl-containing fatty acid react. In the above formula (2), R ¹ represents a residue obtained by removing a hydroxyl group and a carboxyl group from a hydroxyl group-containing fatty acid, and R ² represents a residue obtained by removing an amino group from a diamine. R ³ represents a residue obtained by removing a hydroxyl group and a carboxyl group from a hydroxyl group-containing fatty acid, and R ⁴ represents a residue obtained by removing an amino group from a diamine. R ⁵ represents a residue obtained by removing a carboxyl group from a polybasic carboxylic acid. The average degree of polymerization n is generally about 3 to 5. The number average molecular weight (Mn) is generally about 1000 to 2000.

  As a fatty acid amide available as a commercial item, the thing of a powder state or a paste state is known. The paste is generally diluted with an organic solvent such as xylene or alcohol.

  Examples of the fatty acid amide that can be used in the coating composition of the present invention include the simple substance and mixture of the above-mentioned diamide and polyamide, and specifically, “Flonon HR-2 (of diamide and polyamide) manufactured by Kyoeisha Chemical Co., Ltd. Mixture ") or" Dispalon 6900-20X (diamide) "," Dispalon 6840-10X (mixture of diamide and polyamide) "manufactured by Enomoto Kasei Co., Ltd., and the like.

  Moreover, “Dispalon NS-5210”, “Dispalon NS-5310” manufactured by Enomoto Kasei Co., Ltd., which is commercially available as a mixture of fatty acid amide and polyethylene oxide, can be used. Since there are a plurality of —OH groups in the molecule of polyethylene oxide, the hydrogen bonds formed slowly between the —NH groups in the fatty acid amide molecule and the oxygen atom of —OH of the polyethylene oxide Join. Thereby, polyethylene oxide is interposed in the net structure of the fatty acid amide and connects the net structures, that is, the net structure of the fatty acid amide is strengthened. Therefore, the fatty acid amide mixed with polyethylene oxide is also preferable.

  In the present invention, when the fatty acid amide (E) is contained in the base coating composition, the blending ratio of the fatty acid amide (E) is 0.1 to 5% by mass, preferably with respect to the solid content of the coating composition resin. It is 0.2-3 mass%. By using the fatty acid amide (E) at this content, the stability of the coating composition can be improved without causing rough skin to the coating film.

Cellulose derivative (F)
The cellulose derivative (F) is not particularly limited, and examples thereof include one or more cellulose derivatives selected from the group consisting of cellulose acetate butyrate, nitrocellulose, cellulose acetate, and cellulose acetate propionate. . The cellulose derivative (F) is more preferably cellulose acetate butyrate from the viewpoint of solubility in resin, expression of viscosity, etc., and the degree of acetylation by the measurement method described in ASTM-D-817 is 1 to 34. Particularly preferred are those having a mass%, a butyrylation degree of 16 to 60 mass%, and a viscosity measured by the measurement method described in ASTM-D-1343 in the range of 0.005 to 20 seconds. When the viscosity is lower than the lower limit, the FF property may be lowered. More preferably, the viscosity is in the range of 0.01 to 5 seconds.

  Examples of the cellulose acetate butyrate include, for example, CAB-551-0.01 (viscosity = 0.01 seconds, butyryl group content = 53%), CAB-551-0.2, manufactured by Eastman Chemical Products. (Viscosity = 0.20 seconds, Butyryl group content = 52%), CAB-531-1 (Viscosity = 1.90 seconds, Butyryl group content = 50%), CAB-500-1 (Viscosity = 1.00) Seconds, butyryl group content = 51%), CAB-500-5 (viscosity = 5.00 seconds, butyryl group content = 51%), CAB-553-0.4 (viscosity = 0.30 seconds, butyryl group) Content = 46%), CAB-381-0.1 (viscosity = 0.10 seconds, butyryl group content = 38%), CAB-381-0.5 (viscosity = 0.50 seconds, butyryl group content) = 38%), CAB-381-2 (viscous = 2.00 seconds, butyryl group content = 38%), CAB-321-0.1 (viscosity = 0.10 seconds, butyryl group content = 31.2%), CAB-171-15S (viscosity = 15) 0.000 seconds, butyryl group content = 17%). In addition, the said cellulose acetate butyrate may use together 1 type (s) or 2 or more types.

  In the present invention, the blending ratio when the cellulose derivative (F) is contained in the base coating composition is preferably 0.1 to 10% by mass based on the resin solid content of the coating composition, and is preferably 0.2 to It is more preferable that it is 7 mass%, and it is still more preferable that it is 0.5-5 mass%. By using the cellulose derivative (F) at this content, the coating workability can be improved.

Fine barium sulfate (G)
The particulate barium sulfate (G) that can be used in the method of the present invention is transparent particulate barium sulfate (G) having a primary particle diameter of 0.1 μm or less. Although barium sulfate is also exemplified as the above-mentioned extender pigment, the fine particle barium sulfate (G) here has a primary particle diameter of 0.1 μm or less. On the other hand, barium sulfate used as an extender has a primary particle size larger than 0.1 μm. The particulate barium sulfate (G) can be suitably used in the base coating composition used in the present invention from the viewpoint of improving the appearance of the coating film, particularly the unevenness due to the glitter pigment.

The fine particle barium sulfate (G) is a transparent fine particle pigment mainly composed of barium sulfate represented by BaSO ₄ , and has a primary particle diameter of about 0.1 μm or less, preferably about 0.001 to 0.08 μm. The thing of the range of is preferable. The primary particle diameter is more preferably in the range of 0.01 to 0.05 μm. If the primary particle size exceeds the upper limit, the transparency and glitter may be lowered, which is not preferred. If the primary particle size is less than the lower limit, the effect of improving the unevenness may be insufficient.

  Specific examples of the particulate barium sulfate (G) include, for example, “Varifine BF-1,” “Same BF-10,” “Same BF-20,” “Same BF-40,” A typical example is a product name manufactured by Sakai Chemical Industry Co., Ltd. The fine-particle barium sulfate (G) can be used by mixing and dispersing the pigment at the same time when dispersing a pigment such as a colored pigment that requires pigment dispersion.

  The content of the particulate barium sulfate (G) is preferably in the range of 1 to 20 mass%, preferably 2 to 17 mass%, based on the solid content of the coating composition in the base coating composition. By using the particulate barium sulfate (G) at this content, it is possible to improve the feeling of unevenness in the appearance of the coating film without deteriorating the skin feeling in the appearance of the coating film.

Other Components The base coating composition used in the present invention can contain other film-forming resins. The other film-forming resin is not particularly limited, and a film-forming resin such as an acrylic resin, a polyester resin, an alkyd resin, an epoxy resin, or a urethane resin can be mentioned as a preferable one. Two or more species can be used in combination.

  Moreover, in order to ensure coating workability | operativity, you may add viscosity control agents other than the said fatty acid amide (E) to the said base coating composition. Examples include cross-linkable or non-cross-linkable resin particles, organic bentonite-based organic acid smectite clay, montmorillonite, inorganic pigments such as aluminum silicate and barium sulfate, and flat pigments that develop viscosity depending on the shape of the pigment. be able to.

  In the base coating composition used in the present invention, in addition to the above components, additives usually added to the coating composition, for example, surface conditioners, thickeners, antioxidants, UV inhibitors, antifoaming agents Etc. can be blended. These amounts are within the well-known range of those skilled in the art.

Preparation of base coating composition The solid content during coating of the base coating composition used in the present invention is 18 to 45 mass%, preferably 21 to 40 mass%. If the upper limit is exceeded, the viscosity may be too high and the appearance of the coating film may be lowered. If the lower limit is not reached, the viscosity may be too low and appearance defects such as familiarity and unevenness may occur. Further, outside this range, the coating composition stability may be lowered.

  The production of the coating composition used in the present invention is not particularly limited, including those described later, and a composition such as a pigment is kneaded and dispersed using a sand grinder mill, kneader or roll mill. All methods well known to those skilled in the art can be used.

Clear coating composition The clear coating composition used in the method of the present invention is a two-part clear coating composition comprising a first package and a second package. The two-part clear coating composition is more preferably a low-temperature curable two-part clear coating composition.

  As an example of the two-component clear coating composition, a combination of an isocyanate compound (X) as the second package and a film-forming resin (Y) having a hydroxyl group as the first package can be given.

  The isocyanate compound (X) that is the second package as the curing agent is not particularly limited, and various isocyanate compounds can be used. Examples of the isocyanate compound include aliphatic isocyanates such as trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate (HDI), and trimethylhexamethylene diisocyanate, 1,3-cyclopentane diisocyanate, 1,4-cyclohexane diisocyanate, 1 , Aliphatic cyclic isocyanates such as 2-cyclohexane diisocyanate, xylylene diisocyanate (XDI), 2,4-tolylene diisocyanate (TDI), aromatic isocyanates such as 2,6-tolylene diisocyanate, isophorone diisocyanate (IPDI), Many cycloaliphatic isocyanates such as norbornane diisocyanate methyl, burettes, nurates, etc. Such bodies and mixtures thereof. Isocyanate compound (X) may be used individually by 1 type, and may mix and use 2 or more types.

  For example, an acrylic resin, a polyester resin, an alkyd resin, or a polyether resin can be used as the film forming resin (Y) having a hydroxyl group, which is the first package, as the main agent. These resins may be used alone or in combination of two or more. As the film-forming resin (Y) having a hydroxyl group, an acrylic resin or a polyester resin is preferably used. This is because these resins are excellent in weather resistance and water resistance, and a coating film having excellent performance can be obtained.

  The film-forming resin (Y) having a hydroxyl group preferably has a solid content hydroxyl value of 20 to 180, more preferably 30 to 160. If the upper limit is exceeded, the water resistance of the coating film may be lowered, and if it is less than the lower limit, the curability of the coating film may be lowered.

  The number average molecular weight of the film-forming resin (Y) having a hydroxyl group is preferably 1000 to 20000, and more preferably 2000 to 15000. When the number average molecular weight is less than 1000, workability and curability may be insufficient. On the other hand, when the number average molecular weight exceeds 20000, the non-volatile content at the time of coating is lowered, and workability may be deteriorated.

  The film-forming resin (Y) having a hydroxyl group preferably has an acid value of 2 to 30 mgKOH / g, and more preferably has an acid value of 3 to 25 mgKOH / g. When the above upper limit is exceeded, the water resistance of the coating film may be lowered, and when it is less than the lower limit, the curability of the coating film may be lowered.

  The compounding ratio of the isocyanate compound (X) to the film-forming resin (Y) having a hydroxyl group can be variously selected depending on the purpose. In the present invention, the equivalent ratio of the isocyanate group (NCO) and the hydroxyl group (OH) (NCO / OH) ) Is preferably used in an amount ranging from 0.6 to 1.5. When the content of the isocyanate compound (X) is less than the above lower limit, the curability may be insufficient. On the other hand, when the content exceeds the upper limit, the cured film may become hard and brittle. It is particularly preferable that the equivalent ratio (NCO / OH) of the isocyanate group (NCO) to the hydroxyl group (OH) is in the range of 0.7 to 1.3. The clear coating composition may be a solvent type or an aqueous type.

As another example of the two-component clear coating composition, the following components:
(A) an acid anhydride group-containing acrylic resin obtained by copolymerizing an acid anhydride group-containing ethylenically unsaturated monomer and an ethylenically unsaturated monomer having no acid anhydride group,
(A) a carboxyl group-containing polyester resin obtained by reacting a polyester polyol having three or more hydroxyl groups with an acid anhydride group-containing compound, and (c) a hydroxyl group-containing ethylenically unsaturated monomer and an epoxy group-containing compound. An acrylic resin having a hydroxyl group and an epoxy group, obtained by copolymerizing an ethylenically unsaturated monomer and an ethylenically unsaturated monomer having neither a hydroxyl group nor an epoxy group,
It is also possible to use a two-component thermosetting resin composition containing
These are components (a) 10 to 70% by mass, components (a) 5 to 70% by mass, and components (c) 10 to 80% by mass (wherein mass% is a two-component thermosetting resin composition). The total solid content mass of the product is preferably 100%).

  The two-component thermosetting resin composition in this case is preferably a two-component clear coating composition in which the components (a) and (b) are the first package and the component (c) is the second package. . In this case, before application, by mixing so that the equivalent ratio of the acid anhydride group component contained in the first package and the epoxy group component contained in the second package is 2/1 to 1/2, Good curability can be expressed.

  The above-described two-component clear coating composition may further contain a viscosity control agent. By including the viscosity control agent, the coating workability can be ensured. As the viscosity control agent, those generally showing thixotropy can be used, for example, those already described in the aqueous base coating composition can be used. Moreover, you may contain a curing catalyst, a surface conditioner, etc. as needed. Furthermore, you may contain a well-known ultraviolet absorber, light stabilizer, antioxidant, etc. Furthermore, known rheology control agents and other surface conditioners may be added, and solvents such as alcohol solvents, aromatic hydrocarbon solvents, ester solvents and ketone solvents are used for viscosity adjustment and the like. You can also.

  Regarding the mixing timing of the two packages in the two-pack type clear coating composition, the first package and the second package may be mixed immediately before use and coated with a normal coating gun. Moreover, you may paint by the method of sending each liquid to a gun with a 2 liquid mixing gun, and mixing with a gun tip.

Substrate The coating film forming method of the present invention can be advantageously used for various substrates such as metals, plastics, foams, etc., particularly metal surfaces, and castings. Especially, it can use especially suitably with respect to the metal product which can be cationic electrodeposition coating. Such a base material can be used as a coated product in the present invention.

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

  Moreover, the electrodeposition coating film may be formed in the base material used for the coating-film formation method of this invention on the steel plate by which chemical conversion treatment was carried out. As an electrodeposition coating composition for forming an electrodeposition coating film, a cation type and an anion type can be used, but a cationic type electrodeposition coating composition is preferable because it provides a laminated coating film excellent in corrosion resistance.

Coating Film Forming Method The coating film forming method of the present invention comprises, on a substrate, an intermediate coating film by an intermediate coating composition, a base coating film by a base coating composition, and a clear coating film by a clear coating composition, in that order. This is a method of forming on-wet and then baking and curing these three types of coatings at once.

  In the present invention, when the intermediate coating composition is applied to an article to be coated such as an automobile body, it is applied by multistage coating by air electrostatic spray coating, preferably by two stages, or by air electrostatic spray coating. And a coating method using a combination of a rotary atomizing electrostatic coating machine called “μμ (micro micro) bell”, “μ (micro) bell” or “metabell”. Can do. By these coating methods, a coating film excellent in coating film appearance can be obtained.

  In the present invention, the film thickness of the dry coating film by the intermediate coating composition varies depending on the desired application, but in many cases, 10 to 60 μm is useful. If the upper limit is exceeded, sharpness may be reduced, or defects such as unevenness or flow may occur during painting. If the lower limit is exceeded, the substrate cannot be concealed and film breakage may occur.

  In the coating film forming method of the present invention, the base coating composition and the clear coating composition are sequentially applied on the uncured intermediate coating film by wet-on-wet, and the base coating film and the clear coating film are formed. Form.

  Similarly to the intermediate coating composition, the base coating composition of the present invention can be applied by air electrostatic spray coating or a rotary atomizing electrostatic coating machine such as Metabell, μμ Bell, μ Bell. The dry film thickness of a base coating film can be set to 5-35 micrometers, Preferably it is 7-25 micrometers. If the film thickness of the base coating film exceeds 35 μm, the sharpness may be deteriorated, or unevenness or flow may occur in the coating film. Neither of these is preferable because a discontinuous state of the film may occur.

  In the method for forming a coating film according to the present invention, the clear coating film that is applied after the base coating film is formed smoothes and protects the unevenness caused by the base coating film and the flickering that occurs when a bright pigment is included. Formed to do. Specifically, as a coating method, it is preferable to form a coating film by the above-described rotary atomizing electrostatic coater such as μμ bell or μbell.

  The dry film thickness of the clear coating film formed from the clear coating composition is generally preferably about 10 to 80 μm, more preferably about 20 to 60 μm. Exceeding the upper limit is not preferable because defects such as cracks and sagging may occur during painting. On the other hand, if the value is below the lower limit, the unevenness of the base may not be concealed.

  The laminated coating film obtained as described above forms a coating film by so-called three-coat one-bake that is simultaneously cured. In this case, the baking and drying furnace can be omitted, which is preferable from the viewpoint of economy and environment.

  A cured coating film having a high degree of crosslinking can be obtained by setting the curing temperature for curing the laminated coating film to 60 to 140 ° C, preferably 80 to 130 ° C. If it exceeds the upper limit, the coating film may become hard and brittle, and if it falls below the lower limit, sufficient curing may not be obtained. The curing temperature in the method of the present invention can be cured at a lower temperature than the curing temperature (about 100 to 200 ° C.) used in a general multilayer coating film forming method.

The curing time for curing the laminated coating film varies depending on the curing temperature, but is about 10 to 30 minutes at 90 to 130 ° C, about 5 to 15 minutes at 120 to 150 ° C, preferably 7 to 10 minutes. Degree. The method of the present invention can not only lower the baking temperature but also shorten the baking and curing time.
For example, the curing time of 18 to 30 minutes at a curing temperature of 140 ° C., which is generally used in the past, can be shortened to 5 to 15 minutes.

  The film thickness of the laminated coating film formed by the present invention is in many cases 30 to 300 μm, preferably 50 to 250 μm. If the upper limit is exceeded, film properties such as a cooling cycle may be lowered, and if the lower limit is not reached, the strength of the film itself may be lowered.

  EXAMPLES Hereinafter, although a specific Example is given and this invention is demonstrated in detail, this invention is not limited by a following example. In the following description, “part” means “part by mass”.

Production Example 1 Production of urethane-modified polyester resin for intermediate coating composition Into a 2 L reaction vessel equipped with a nitrogen introduction tube, a stirrer, a temperature controller, a dropping funnel and a cooling tube equipped with a decanter, 440 parts of isophthalic acid, hexa 20 parts of hydrophthalic acid, 40 parts of azelaic acid, 300 parts of trimethylolpropane and 200 parts of neopentyl glycol were charged. When the raw materials were dissolved and stirred by heating, 0.2 parts of dibutyltin oxide was added and stirred. The reaction layer temperature was gradually raised from 180 to 220 ° C. over 3 hours. The resulting condensed water was distilled out of the system. When the temperature reached 220 ° C., the temperature was kept for 1 hour, 20 parts of xylene was gradually added into the reaction layer, and the condensation reaction was allowed to proceed in the presence of a solvent. When the resin acid value reached 10 mgKOH / g, it was cooled to 100 ° C., and 100 parts of hexamethylene diisocyanate was gradually added over 30 minutes. Further, after holding for 1 hour, 200 parts of xylene and 200 parts of butyl acetate were added, and the solid content was 70%, the number average molecular weight was 2000, the acid value was 8 mgKOH / g (solid content), the hydroxyl value was 120 (solid content), A urethane-modified polyester resin was obtained.

Production Example 2 Production of Non-Water Dispersion for Intermediate Coating Composition (a) Production of Dispersion Stabilizing Resin 90 parts of butyl acetate was charged in a container equipped with a stirrer, a temperature controller, and a reflux condenser. Next, 20 parts of a solution composed of 38.9 parts of methyl methacrylate, 38.8 parts of stearyl methacrylate, 22.3 parts of 2-hydroxyethyl acrylate and 5.0 parts of azobisisobutyronitrile were added and stirred. While heating, the temperature was raised. The remaining 85 parts of the above mixed solution was added dropwise at 110 ° C. over 3 hours, and then a solution consisting of 0.5 parts of azobisisobutyronitrile and 10 parts of butyl acetate was added dropwise over 30 minutes. The reaction solution was further stirred and refluxed for 2 hours to increase the rate of conversion to resin, and the reaction was terminated to obtain an acrylic resin having a solid content of 50% and a number average molecular weight of 5600.

(B) Production of non-aqueous dispersion 90 parts of butyl acetate in a container equipped with a stirrer, a cooler and a temperature control device, 120 parts of acrylic resin obtained by the production of (a) dispersion-stable resin (60 parts as solid content) ). Next, 7.0 parts of styrene, 1.8 parts of methacrylic acid, 12.0 parts of methyl methacrylate, 8.5 parts of ethyl acrylate, 40.7 parts of 2-hydroxyethyl acrylate, and 1.4 parts of azobisisobutyronitrile. Then, a solution consisting of 0.1 parts of azobisisobutyronitrile and 1 part of butyl acetate was added dropwise over 30 minutes. When the reaction solution was further stirred for 1 hour, an emulsion having a solid content of 60% and a particle size of 180 nm was obtained. This emulsion was diluted with butyl acetate to obtain a core-shell type butyl acetate dispersion having a viscosity of 300 cps (25 ° C.) and a particle diameter of 180 nm and a non-aqueous dispersion content of 40% by mass. The non-aqueous dispersion resin had a Tg of 23 ° C. and a hydroxyl value of 162 (solid content).

Production Example 3 Production of Intermediate Coating Composition 1 To 1 L vessel, 107 parts of urethane-modified polyester resin varnish for intermediate coating composition obtained in the previous production example, CR-97 (Ishihara Sangyo Titanium Oxide) 280 Parts, MA-100 (Mitsubishi Chemical Corporation carbon black pigment) 13 parts, LMS-100 (Fuji talc scale talc) 7 parts, butyl acetate 47 parts and xylene 47 parts, GB503M of the same amount as the charged mass (Glass beads having a particle diameter of 1.6 mm) were charged and dispersed at room temperature for 3 hours using a tabletop sand grinder mill to obtain a gray pigment paste. The particle size at the end of dispersion by a grind gauge was 5 μm or less. The glass beads were filtered to obtain a pigment paste.

  To 100 parts of the pigment paste, 130 parts of the urethane-modified polyester resin for the intermediate coating composition, 53 parts of a non-aqueous dispersion for the intermediate coating composition of the above production example, Uban 128 (Melamine resin manufactured by Mitsui Chemicals, solid content) 60 parts) and 71 parts of Duranate MF-K60X (active methylene type blocked isocyanate manufactured by Asahi Kasei Corporation, solid content 60%) were mixed to prepare an intermediate coating composition 1.

  Further, a mixed solvent of ethoxyethyl propionate / S-100 (Aromatic hydrocarbon solvent manufactured by Exxon) = 1/1. The dilution was adjusted to 19 seconds / 20 ° C. using a 4 Ford cup. The nonvolatile content at the time of application was 49%.

Production Example 4 Production of urethane-modified polyester resin for base coating composition 334 parts of isophthalic acid, hexahydrophthalate in a 2 L reaction vessel equipped with a nitrogen introducing tube, a stirrer, a temperature controller, a cooling tube equipped with a dropping funnel and a decanter 311 parts of acid, 57 parts of ethylene glycol, 105 parts of trimethylolpropane and 289 parts of neopentyl glycol were charged. When the raw materials were dissolved and stirred by heating, 0.2 parts of dibutyltin oxide was added and stirring was started. The reaction layer temperature was gradually raised from 180 to 220 ° C. over 3 hours. The resulting condensed water was distilled out of the system. When the temperature reached 220 ° C., the temperature was kept for 1 hour, 20 parts of xylene was gradually added into the reaction layer, and the condensation reaction was allowed to proceed in the presence of a solvent. When the resin acid value reached 8 mgKOH / g, it was cooled to 100 ° C., and 10 parts of hexamethylene diisocyanate was gradually added over 30 minutes. Further, after holding for 1 hour, 344 parts of xylene, 43 parts of butyl acetate and 43 parts of n-butanol were added, 70% solid content, number average molecular weight 1800, weight average molecular weight 10,000, acid value 6 mgKOH / g (solid content), hydroxyl group A urethane-modified polyester resin having a valence of 100 (solid content) was obtained.

Production Example 5 Production of acrylic resin for base coating composition 50 parts of xylene and 14 parts of n-butanol were added to a 1 L reaction vessel equipped with a nitrogen introducing tube, a stirrer, a temperature controller, a dropping funnel and a cooling tube equipped with a decanter. The temperature was set to 110 ° C. Next, 5 parts of styrene, 35.3 parts of ethyl acrylate, 41.1 parts of butyl methacrylate, 15.5 parts of hydroxyethyl acrylate, 3.1 parts of methacrylic acid, and t-butylperoxy-2-ethylhexanoate 4. The solution mixed with 0 part was added dropwise over 3 hours. Next, a solution consisting of 1.0 part of t-butylperoxy-2-ethylhexanoate and 6 parts of xylene was added dropwise over 30 minutes, and then kept at 110 ° C. for 1 hour. An acrylic resin having a solid content of 60%, an acid value of 20 mg KOH / g (solid content), a hydroxyl value of 75 (solid content) and a number average molecular weight of 5000 was obtained.

Production Example 6 Production of Solvent Type Metallic Base Coating Composition 1 In a stainless steel container, AS-9606 (urea modified acrylic resin manufactured by Mitsubishi Rayon Co., urea modified amount 6.5%, acid value 12 mgKOH / g (solid content), hydroxyl value 70 parts (solid content), weight average molecular weight 7000, Tg 16 ° C.) 75 parts, 14.3 parts urethane modified polyester for base coating composition of the above production example, 25 parts of acrylic resin for base coating composition of the above production example 2.9 parts of Blue G-314 (Sanyo Color Co., Ltd. Blue Pigment) and 6.0 parts of Varifine BF-40 (Sakai Chemical Co., Ltd. Barium Sulfate Pigment) were dispersed in a pigment so that the respective particle sizes were 5 μm or less. 33.9 parts of the obtained pigment dispersion paste, 50 parts of Uban 20N60 (Butylated melamine resin manufactured by Mitsui Chemicals, solid content 60%), aluminum paste 640NS was weighed (Toyo Aluminum Co., Ltd. aluminum pigment) 11.6 parts, was stirred at tabletop stirrer, solvent-borne metallic thin blue base paint composition 1 (PWC17.0%) was prepared.

  Next, the solvent-type metallic base coating composition 1 was diluted with a thinner thinner consisting of 10 parts of Solvesso 150 (hydrocarbon solvent manufactured by Exxon Petroleum), 40 parts of ethyl acetate, 40 parts of toluene and 10 parts of butyl acetate. . The dilution was adjusted to 12.5 seconds / 20 ° C. with a 4 Ford cup.

Example 1

Formation of multilayer coating film Cation electrodeposition coating composition “V-50” (manufactured by Nippon Paint Co., Ltd.) is cured on a 30 mm long, 40 cm wide, 0.8 mm thick dull steel sheet that has been subjected to zinc phosphate conversion treatment. Is electrodeposited so as to be about 20 μm, heated at 160 ° C. for 30 minutes to be cured, and then subjected to air spray coating so that the intermediate coating composition 1 of the above production example has a cured film thickness of about 25 μm. And left for 7 minutes.

  Next, the substrate to be coated that has been degreased with a solvent is erected vertically, and the above-mentioned metallic base coating composition 1 is “Metabell” (Lansberg) in two stages at intervals of 2 minutes so that the dry film thickness becomes 15 μm. The coating was made by a rotary atomizing electrostatic coater. A base coating film was prepared by allowing to stand at room temperature for 4 minutes.

  Then, after mixing in advance and stirring well, No. A two-pack type clear coating composition “R298 Clear” (an isocyanate curable clear coating composition, trade name) manufactured by Nippon Bee Chemical Co., Ltd., diluted to 25 seconds / 20 ° C. with a 4 Ford cup, The coating was applied once so that the dry coating thickness was 40 μm. Next, after standing at room temperature for 7 minutes in a vertical state, the film was baked in a 120 ° C. drier for 30 minutes in the vertical state. A laminated coating film was obtained by 3-coat 1-bake coating.

The intermediate coating film is formed in the same procedure as that used for forming the laminated coating film on which the metallic base single-layer coating film for comparison is formed, and the solvent-based metallic base previously produced is formed on this intermediate coating film. The coating composition 1 was applied to a dry film thickness of 15 μm by the same method as described above to prepare a coated plate having only a metallic base coating film (no clear coating film). Next, after standing for 7 minutes vertically at room temperature, it was baked in a dryer at 120 ° C. for 30 minutes in the vertical state to form a metallic base single layer coating film.

  Evaluation of the obtained laminated coating film was implemented in accordance with the following evaluation methods.

<Flip-flop (FF)>
The obtained laminated coating film was measured for F value using a variable angle color difference meter “Multi-Angle Spectrophotometer MA68 II” (manufactured by X-Rite Co.) to evaluate the flip-flop property (FF property). It shows that it is excellent in FF property, so that a value is large.

<Color return>
Based on the metallic base single layer coating film, the color difference (ΔE) with the multilayer coating film obtained by the 3-coat 1-bake coating method was measured, and the value of the color difference was evaluated as the color reversibility. A smaller value indicates that color reversion does not occur and color reversibility is excellent.

<Dense feeling>
The glitter feeling when the obtained multilayer coating film was viewed almost directly in front (highlight portion) was visually evaluated. The results are shown by the following criteria.
3; Dense feeling of glittering pigment is not felt, and dense glittering feeling is remarkable 2; Dust feeling of glittering pigment is not felt, and there is little dense glittering feeling 1; Particles of glittering pigment The feeling is conspicuous and there is no dense glitter

<Appearance>
The finished appearance of the laminated coating film was measured with a wave scan (manufactured by Big Chemie-Gardner Company), and evaluated based on a measured value (W2 value) in a medium wavelength region of 800 to 2400 μm. The smaller the value, the better the appearance (skin feel).

Example 2
Preparation of clear paint composition
Synthesis of acid anhydride group-containing acrylic resin (component (a))
46.5 parts by mass of propylene glycol monomethyl ether acetate and 51.8 parts by mass of Solvesso 100 (aromatic hydrocarbon solvent manufactured by Esso) in a reaction vessel equipped with a thermometer, a stirrer, a cooling pipe, a nitrogen introduction pipe, and a suitable funnel Was heated to 130 ° C. In the above container, using a suitable funnel, 16.4 parts by mass of styrene monomer, 18.86 parts by mass of n-butyl acrylate, 7.7 parts by mass of isobornyl acrylate, 22.53 parts by mass of cyclohexyl methacrylate, acrylic acid Solvesso 100 of 13.94 parts by weight of 2-ethylhexyl, 18 parts by weight of maleic anhydride and 2.57 parts by weight of acrylic acid, and 8.5 parts by weight of t-butylperoxy 2-ethylhexanoate and 5.2 parts by weight The solution consisting of was applied over 3 hours. After maintaining at 130 ° C. for 30 minutes after the completion of dropping, a solution composed of 1 part by mass of t-butylperoxy 2-ethylhexanoate and 2.2 parts by mass of Solvesso 100 was added dropwise over 30 minutes. After completion of the dropping, the reaction was continued at 130 ° C. for another hour, and the nonvolatile content containing the acid anhydride group-containing acrylic resin having a number average molecular weight of 3100 and an acid anhydride group of 1.84 mmol / g (solid content). 58% varnish was obtained.

Synthesis of carboxyl group-containing polyester resin (component (I))
In a reaction vessel equipped with a thermometer, a stirrer, a cooling tube, and a nitrogen introduction tube, 8.85 parts by mass of pentaerythritol, Plaxel M (ε-caprolactone monomer, trade name, manufactured by Daicel), 57.5 parts by mass, Ricacid HH-A ( New Nippon Rika Co., Ltd. hexahydrophthalic anhydride (trade name) 33.92 parts by mass and dibutyltin oxide 0.1 part were charged and heated to 150 ° C. After holding at 150 ° C. for 2 hours, 616 parts of hexahydrophthalic anhydride dissolved by heating was added, kept at 150 ° C. for 1 hour, cooled, and 33.4 parts by mass of 3-ethoxyethyl propionate And a carboxyl group-containing polyester resin having a number average molecular weight of 2500, a weight average molecular weight / number average molecular weight of 1.3, a carboxyl group of 2.2 mmol / g (solid content) and a hydroxyl group of 0.32 mmol / g (solid content). A varnish having a non-volatile content of 75% was obtained.

Synthesis of acrylic resin containing hydroxyl group and epoxy group (component (c))
Into an autoclave equipped with a thermometer, a stirrer, a condenser tube, a nitrogen inlet tube, and a suitable funnel, 23.7 parts by mass of 3-ethoxyethyl propionate was charged and heated to 170 ° C. In the above reaction tank, using a liquid feed pump, styrene 25 parts by mass, glycidyl methacrylate 30.3 parts by mass, n-butyl acrylate 8 parts by mass, isobornyl acrylate 23.9 parts by mass, 4-hydroxybutyl acrylate 12 .8 parts by mass and a solution consisting of 3.0 parts of di-tert-amyl peroxide and 2.6 parts of 3-ethoxyethylpropionate were added dropwise over 3 hours.

  After maintaining at 170 ° C. for 30 minutes after the completion of dropping, a solution consisting of 0.4 parts of di-tert-butyl peroxide and 1.5 parts of 3-ethoxyethyl propionate was added over 30 minutes using a liquid feed pump. It was dripped. After completion of the dropping, the reaction was continued at 170 ° C. for another hour, and then an acrylic having a number average molecular weight of 2200, an epoxy group of 2.1 mmol / g (solid content), and a hydroxyl group of 0.9 mmol / g (solid content). A varnish having a nonvolatile content of 76% containing a resin was obtained.

Preparation of Clear Coating Composition 1 In a stainless beaker, 32 g of resin solid content of the prepared acid anhydride group-containing acrylic resin (component (A)), resin solid content of the prepared carboxyl group-containing polyester resin (component (I)) 15 g and 0.5 part of tetrabutylammonium bromide curing catalyst were mixed to obtain a first package.

  On the other hand, 53 g as the resin solid content of the prepared acrylic resin (component (U)), 2 parts of UV absorber “Tinuvin 900” manufactured by Ciba Specialty Co., Ltd., light stabilizer “Sanol LS-440” manufactured by Sankyo Co., Ltd. 1 part and 0.1 part of a surface conditioner “Modaflow” manufactured by UCB were mixed to obtain a second package. If stored in the state of these two liquids, no reaction occurs at room temperature. The first package and the second package obtained above were mixed immediately before use and mixed with a mixed solvent consisting of butyl acetate / xylene = 1/1. 4 and the viscosity was adjusted to 28 seconds.

  A laminated coating film was formed in the same manner as in Example 1 except that the two-component clear coating composition thus obtained was used. The obtained laminated coating film was evaluated in the same manner as in Example 1.

Comparative Example 1
A laminated coating film was formed in the same manner as in Example 1 except that Superlac M-350 metallic paint (baked metallic paint manufactured by Nippon Paint Co., Ltd.) was used as the base paint composition. The obtained laminated coating film was evaluated in the same manner as in Example 1.

Comparative Example 2
Laminated coating film in the same manner as in Example 1 except that Superlac O-150 clear coating composition (melamine curable one-part clear coating composition manufactured by Nippon Paint Co., Ltd.) was used as the clear coating composition. Formed. The obtained laminated coating film was evaluated in the same manner as in Example 1.

  The laminated coating film formed by 3-coat 1-bake using the intermediate coating composition, the light blue solvent-based metallic base coating composition and the clear coating composition obtained in Examples 1 and 2 described above was It was excellent in glossiness) and transparency. The laminated coating film was also an excellent coating film having a small peel area in appearance and a low peeling frequency even when it was subjected to chipping. Furthermore, the obtained multilayer coating film has a feeling of fine radiance that cannot be obtained with conventional medium-color paints, especially in the case where the lustrous pigment is uniformly dispersed, among the appearance evaluation items. Met. Further, this laminated coating film was excellent in the FF feeling in which the metallic feeling remarkably changes depending on the viewing angle.

  On the other hand, the multilayer coating films obtained by Comparative Examples 1 and 2 were particularly inferior in coating film appearance (W2) as compared with the multilayer coating films of Examples. Moreover, the laminated coating film of Comparative Example 1 was inferior to the laminated coating film of the Examples in terms of FF property, denseness, and color return.

  According to the present invention, a laminated coating film can be formed without causing color reversion due to the mixing of the metallic base coating film and the clear coating film and the deterioration of the coating film appearance. The method of the present invention is a method for forming a coating film by a three-coat one-bake system that is economical and has a low environmental impact. Thus, the method of the present invention is an industrially excellent method and can form a laminated coating film having an excellent coating film appearance.

Claims (6)

An intermediate coating composition, a base coating composition, and a clear coating composition are sequentially applied on a substrate on which an electrodeposition coating film is formed by wet-on-wet to form a coating film. A method for forming a laminated coating film comprising a step of baking and curing layers simultaneously,
The base coating composition has the following components:
Urea-modified acrylic resin (A) 20-65 mass%;
5 to 40% by mass of a urethane-modified polyester resin (B) obtained by polycondensation of a hydroxyl group-containing polyester resin and a diisocyanate compound and having a weight average molecular weight (Mw) of 2000 to 20000;
Melamine resin (C) 10 to 40% by mass;
However, the amounts of (A) to (C) are based on the coating composition resin solid mass; and the pigment concentration (PWC) of the glitter pigment (D) is 1 to 23.0%, provided that the coating composition solid mass is Based on:
A solvent-based base coating composition comprising:
The solid mass ratio of the urea-modified acrylic resin (A) and the urethane-modified polyester resin (B) is 60/40 to 95/5, and the clear coating composition is a two-pack type clear coating composition Is,
Laminated coating film forming method. The intermediate coating composition has the following components:
A hydroxyl group-containing polyester resin obtained by polycondensation of an acid component containing 80 mol% or more of isophthalic acid and a polyhydric alcohol and having a glass transition point (Tg) of 40 to 80 ° C. is reacted with an aliphatic diisocyanate compound. The urethane-modified polyester resin (i) having a number average molecular weight (Mn) of 1500 to 3000, obtained by 40 to 56% by mass;
Melamine resin (ii) 10-30% by mass;
Blocked isocyanate compound (iii) 15-30% by mass, in which an isocyanate compound obtained by reacting with hexamethylene diisocyanate or hexamethylene diisocyanate and a compound that reacts with it is blocked with a compound having an active methylene group;
4-15% by mass of a non-aqueous dispersion resin (iv) having a core-shell structure;
However, the amounts of (i) to (iv) are based on the solid content of the coating composition resin. And 0.4-2 parts by mass of a flat pigment (v) having a major axis of 1-10 μm and a number average particle size of 2-6 μm, provided that the coating composition resin solid content is 100 parts by mass;
An intermediate coating composition containing
The method for forming a laminated coating film according to claim 1.   The base coating composition further comprises fatty acid amide (E) 0.1 to 5% by mass; cellulose derivative (F) 0.1 to 10% by mass; and particulate barium sulfate (G) 1 to 20% by mass (provided that The amount of (E) to (F) is based on the resin solid mass, and the amount of (G) is based on the solid mass of the coating composition). The method for forming a laminated coating film according to claim 1 or 2. The two-component clear coating composition is
An isocyanate compound (X), and a film-forming resin having a hydroxyl group (Y),
The method for forming a laminated coating film according to any one of claims 1 to 3, which is a two-component clear coating composition containing The two-component clear coating composition is
(A) an acid anhydride group-containing acrylic resin obtained by copolymerizing an acid anhydride group-containing ethylenically unsaturated monomer and an ethylenically unsaturated monomer having no acid anhydride group,
(A) a carboxyl group-containing polyester resin obtained by reacting a polyester polyol having three or more hydroxyl groups with an acid anhydride group-containing compound, and (c) a hydroxyl group-containing ethylenically unsaturated monomer and an epoxy group-containing compound. An acrylic resin having a hydroxyl group and an epoxy group, obtained by copolymerizing an ethylenically unsaturated monomer and an ethylenically unsaturated monomer having neither a hydroxyl group nor an epoxy group,
The method for forming a laminated coating film according to any one of claims 1 to 3, which is a two-component clear coating composition containing   A coated article having a multilayer coating film obtained by the method for forming a multilayer coating film according to any one of claims 1 to 5.