JPH0699661B2 - Topcoat paint composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel coating composition for top coating, and more particularly to a coating composition for top coating capable of forming a coating film having excellent scratch resistance.

Conventional technology and its problems Conventionally, the top coating film that has been applied to the outer panels of automobiles is liable to be scratched due to collisions such as sand and dust during traveling or friction due to car wash brushes, etc. This is one of the causes of the above, and scratches are very conspicuous especially in a dark color coating film such as black, navy blue, or brown.

Means for Solving the Problems The present inventors have found that the coating film has physical or chemical performance, smoothness,
Studies were conducted to develop a coating composition capable of forming a coating film having improved scratch resistance and capable of high-quality appearance finish without lowering the image clarity and weather resistance. As a result, they have found that the above object can be achieved by using a low molecular weight polyol having a narrow molecular weight distribution in combination with a polyester having a specific composition and using a monomeric alkoxymelamine resin as a crosslinking agent, and completed the present invention.

That is, the present invention provides (A) a weight average molecular weight of 400 to less than 2000, and a ratio w / weight average molecular weight (w) to number average molecular weight (n) w /
a low molecular weight polyol component having a molecular weight distribution of n of 1.6 or less and a hydroxyl value of 150 to 400 mgKOH / g, (B) a weight average molecular weight of 2,000 to 50,000, and a hydroxyl value of 5
A polyester resin having a cyclohexylene ring content of 0 to 200 mgKOH / g and a cyclohexylene ring content of 7% by weight or less, and (C) an alkoxymonomeric melamine. Based on the total weight of the components, (A) component is 15 to 60% by weight and (B) component is 15% by weight.
To 60% by weight and 20 to 50% by weight of the component (C), the present invention relates to a coating composition for topcoating.

As a method to improve the scratch resistance of the coating film, for example, the coating film should have a pencil hardness of 4H or more to increase scratch resistance and prevent scratches. A method of lowering the coefficient so that the contact substance on the coating film slides to prevent scratches, and the load of scraping is received as elastic deformation of the coating film, and when the load is removed, the deformation is quickly recovered and the scratches are formed. There are three possible ways to prevent this.

However, it is difficult to form a hard organic coating film of 4H or more with the above-mentioned a, and even if a coating film can be formed, the coating film is poor in flexibility, internal stress is large, and cracking occurs. However, the friction coefficient of the coating film surface can be easily lowered by adding a substance that orients to the coating film surface to lower the friction coefficient.
In this method, the effect of preventing scratches is lost when the substance is lost from the surface of the coating film, and the durability is extremely short. Also,
As a method of (c), a composition using an isocyanate as a curing agent has been tried so far, but this has not been put to practical use because of insufficient scratch resistance.

The composition of the present invention is one of the methods (a) to (c) among the above-mentioned methods (a) to (c), which is a method which has never been carried out.

In the composition of the present invention, the component (A) has a low molecular weight and a narrow distribution. Also, (C)
The component also has a low molecular weight and hardly self-condenses. Therefore, the three-dimensional cured product of the component (A) and the component (C) has a short inter-crosslinking distance and forms a regular network, and is a microscopically elastic elastic material with excellent recoverability. Form a coating film. As a result, the coating film responds to the load of abrasion as an elastic body and does not lead to destruction,
It is absorbed as elastic deformation, and when the load is removed, the deformation recovers, resulting in no scratching.

However, a coating film consisting only of the above-mentioned components (A) and (C) does not have sufficient performance as a coating film for automobile outer panels, for example, acid resistance, impact resistance, sharpness, etc. In order to improve, the component (B) is used within a range that does not reduce the scratch resistance.

Conventionally, car skins that have been finished in dark colors such as black, blue, green, and red are scratched when they are scratched due to collision with running sand or dust or friction from a car wash brush. Because it is easy to see, it was avoided to finish with such a paint color, but recently, due to diversification of tastes of car buyers and improvement of commercialability, intensification of competition not only in Japan but also overseas, It has become essential to design paints that avoid these color gamuts.

The coating composition of the present invention is extremely excellent in scratch resistance and solves the problem of scratches in the above-mentioned coating color design, and has a very great technical effect.

The coating composition of the present invention will be specifically described.

The component (A) has a weight average molecular weight of 400 to less than 2000, and has a molecular weight distribution in which the ratio w / n of the weight average molecular weight (w) to the number average molecular weight (n) is 1.6 or less, and the hydroxyl value is Is a low molecular weight polyol component having a content of 150 to 400 mg KOH / g.

Generally, the molecular weights of the products synthesized by the polymerization reaction, the condensation reaction, the addition reaction, etc. are not all the same and are distributed in a certain range. Although various kinds of average molecular weights are defined as the average molecular weight of such a substance, there are most commonly a weight average molecular weight (w) and a number average molecular weight (n). As a characteristic value representing the breadth of the molecular weight distribution, w / n is often used. In the case where there is no molecular weight distribution and there is complete monodispersion, w / n = 1, and the larger the molecular weight distribution, the larger. The acrylic resin, alkyd resin, and polyester resin for ordinary paints have w / n in the range of 2 to 8.

In the present invention, the weight average molecular weight (w), number average molecular weight (n) and w / n of the components (A) and (B) are
Is measured by gel permeation chromatography (GPC) in which a calibration curve was prepared using polystyrene as a standard substance.

It is important that the component (A) has a weight average molecular weight of 400 to less than 2000, preferably 500 to 1800. When the weight average molecular weight is less than 400, the coating performance such as weather resistance is deteriorated and the evaporation rate at the time of baking is increased, which causes a problem in equipment maintenance, which is not preferable. On the other hand, if the weight average molecular weight is 2000 or more, the cross-linking density of the coating film becomes insufficient and it becomes difficult to obtain a coating film excellent in scratch resistance, which is not preferable.

The state of the molecular weight distribution of the component (A) is also important. That is, in the present invention, it is necessary to have a narrow molecular weight distribution, and the ratio of the weight average molecular weight to the number average molecular weight (w /
n) is 1.6 or less, preferably 1.4 or less. w / n
Is more than 1.6, the scratch resistance of the resulting coating film is deteriorated, which is not preferable. It is considered that the scratch resistance is lowered because the molecular weight distribution between cross-linking points becomes non-uniform and the microscopic elastic deformation necessary for the scratch resistance is not exhibited.

Examples of the low molecular weight polyol component having such a molecular weight distribution include those exemplified in the following (i) to (iv).

(I) A polyester polyol which is a branched polyester polyol obtained by condensing an organic acid component and an alcohol component used in the production of ordinary polyester resins for coating materials as raw materials, and has a molecular weight and a molecular weight distribution within the above range.

Among the organic acid components used in the production of such polyester,
Examples of the polybasic acid include phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, tetrahydroterephthalic acid, hexahydrophthalic acid, hexahydroisophthalic acid, hexahydroterephthalic acid, hettic acid, trimellitic acid, hexahydrotrimellitic acid. Acid, pyromellitic acid, cyclohexanetetracarboxylic acid, methyltetrahydrophthalic acid, methylhexahydrophthalic acid, endomethylenehexahydrophthalic acid, methylendomethylenetetrahydrophthalic acid, maleic acid, fumaric acid, itaconic acid, succinic acid, glutaric acid , Adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, suberic acid, pimelic acid, dimer acid (a dimer of tall oil fatty acid), tetrachlorophthalic acid, naphthalenedicarboxylic acid, 4,4 '
-Diphenylmethanedicarboxylic acid, 4,4'-dicarboxybiphenyl and the like, their acid anhydrides and dialkyl esters, especially dimethyl ester and the like can be mentioned.

Examples of the dihydric alcohol in the alcohol component include ethylene glycol, propylene glycol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-butanediol and 1,5-pentane. Diol, 1,
4-pentanediol, 2,4-pentanediol, 2,3-
Dimethyl trimethylene glycol, 3-methyl-pentane-1,5-diol, 3-methyl-4,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,6
-Hexanediol, 1,5-hexanediol, 1,4-hexanediol, 2,5-hexanediol, 1,4-cyclohexanedimethanol, diethylene glycol, dipropylene glycol, triethylene glycol, neopentyl glycol, hydroxypivalic acid Examples include neopentyl glycol ester, polyalkylene oxide, bishydroxyethyl terephthalate, and alkylene oxide adduct of (hydrogenated) bisphenol A. Also, a monoepoxy compound such as Cardura E10 (manufactured by Shell Chemical Co., Ltd.), α-olefin epoxide, butylene oxide can be used as one kind of glycol.

Examples of the trihydric or higher polyhydric alcohol include glycerin, trimethylolpropane, trimethylolethane,
Examples thereof include diglycerin, pentaerythritol, dipentaerythritol and sorbitol.

Also, a compound having both a carboxylic acid and a hydroxyl group in the molecule can be used. Examples of such compounds include dimethylolpropionic acid, pivalic acid, 12-hydroxystearic acid and ricinoleic acid. Lactones such as ε-caprolactone and γ-valerolactone are also cyclic ester compounds and therefore belong to the category of the above compounds.

In addition to these, various monofunctional raw materials such as natural and synthetic higher fatty acids, higher alcohols, benzoic acid and pt-butylbenzoic acid, and natural oils can be used in combination.

The low molecular weight polyester polyol is branched.
In order to have a branched structure, it is necessary to include a polyhydric alcohol having a valence of 3 or more and / or a polybasic acid in the raw material used.

In producing a branched low-molecular-weight polyester polyol having the above-mentioned molecular weight and molecular weight distribution using the above-mentioned raw materials, it may be sufficient to adopt a method for producing a normal polyester, but in many cases However, the synthetic method requires the following special measures for selection of raw materials, purification of products, and the like. As a device of the synthesis method,
For example, in the presence of a suitable catalyst such as p-toluenesulfonic acid or monobutyltin hydroxide, a large amount of an inert solvent having a high boiling point (for example, a solvent mainly composed of alkylbenzene having a boiling point of about 130 to 250 ° C.) (for example, polyester resin component 10
It is preferable that the polyester polyol is present in an amount of about 30 to 150 parts by weight per 0 parts by weight and the solvent is refluxed in a solution state for a long time (for example, 15 to 40 hours) to synthesize the polyester polyol. By this method, the molecular weight distribution of the obtained polyester polyol can be narrowed. In addition, as a method of selecting a raw material, for example, a raw material that can be synthesized by using only an addition reaction with a fast reaction rate (for example, Cardura E10 (manufactured by Shell Chemical Co.) and trimellitic acid, phthalic anhydride and trimethylolpropane, etc.) If selected, the molecular weight distribution can be sharpened. More specifically, for example, by adding 3 mol of a monoepoxy compound to 1 mol of trimellitic acid, a polyester polyol having a narrow molecular weight distribution can be obtained. Further, in the purification of the product, for example, a method of fractional precipitation in which a suitable poor solvent (for example, petroleum ether) is added to a solution of a low molecular weight polyester polyol (cutting of a high molecular weight component), a low molecular weight polyester polyol solution in a large amount of a poor solvent Reprecipitation method to add resin to precipitate resin (cut low molecular weight components), depressurize under heating to remove low molecular weight components by evaporation, supercritical state (Super Crit
The solubility of the resin in the medium in the ical state) can be classified by utilizing the fact that the solubility of the resin greatly changes depending on the pressure and the temperature.

Further, in order to set w within the range of 400 to less than 2000, the polybasic acid in the raw material is used in a molar ratio of about 0.4 to the polyhydric alcohol.
It may be set within the range of to 0.75.

Among the low molecular weight branched polyester polyols, preferred are, for example, cyclohexanedimethanol, trimethylolpropane, and anhydrous amber which are synthesized by using monobutyltin hydroxide as a catalyst in Swazol-1500 (produced by Cosmo Oil Co., Ltd., aromatic petroleum solvent). Examples thereof include low molecular weight branched polyester polyols composed of an acid and adipic acid.

(Ii) A polyester polyol which is a straight-chain type polyester polyol using a raw material used for the production of ordinary polyester resins for paints and has a molecular weight and a molecular weight distribution within the above range.

As a raw material used for producing such a polyester polyol, any of the raw materials obtained by removing the polyhydric alcohol having a valence of 3 or more and the polybasic acid from the raw materials listed in (i) above can be used.

In producing the linear polyester polyol having the above-mentioned molecular weight and molecular weight distribution, there are cases where it is sufficient to adopt the method for producing an ordinary polyester, as described in (i) above.
However, the special method shown in (i) above may be appropriately used for the synthesis method, selection of raw materials, purification of the product, etc.

Among the linear polyester polyols, as a suitable one, for example, a polyester composed of hexahydrophthalic anhydride, adipic acid and neopentyl glycol is synthesized by a usual method and then depressurized at high temperature for a long time (specifically,
230-240 ℃), about 5-10 hours, pressure reduction of about 20mmHg or less)
A polyester polyol obtained by removing the low molecular weight component by evaporation can be mentioned.

(Iii) A polyol having a ring-opening polyester polyol obtained by ring-opening polymerization of a lactone with a divalent or higher polyhydric alcohol as an initiator, and having a molecular weight and a molecular weight distribution within the above range.

The lactones used include, for example, ε-caprolactone, β-methyl-δ-valerolactone, γ-valerolactone, δ-caprolactone, γ-caprolactone, γ.
-Metervalerolactone, β-propiolactone, γ-
Butyrolactone and the like can be mentioned. Examples of the polyhydric alcohol as an initiator include ethylene glycol, diethylene glycol, 1,4-butanediol, 1,6-hexanediol, 3-methyl-pentane-1,5-diol, glycerin, trimethylolethane and triethyl alcohol. Methylolpropane, pentaerythritol and the like can be mentioned. Examples of the catalyst used in the ring-opening polymerization include boron trifluoride-ethyl etherate, sulfuric acid, phosphoric acid, tetraisopropyl titanate, tetrabutyl titanate, dibutyltin oxide, hydroxytitanium stearate, isopropyl titanium stearate, litharge, etc. Is mentioned.

In producing the ring-opening polyester polyol having the above-mentioned molecular weight and molecular weight distribution, a polyol having a narrow molecular weight distribution can be obtained only by adopting an ordinary ring-opening polymerization method. The special device shown in i) can also be used as appropriate.

Among the above ring-opened polyester polyols, for example, a polyol obtained by adding 5 mol of ε-caprolactone to 1 mol of ethylene glycol, a polyol obtained by adding 6 mol of ε-caprolactone to 1 mol of trimethylolpropane, and the like can be mentioned. .

(Iv) An acrylic polyol which is a copolymer of a hydroxyl group-containing monomer and a monomer copolymerizable therewith and has a molecular weight and a molecular weight distribution within the above range.

Examples of the hydroxyl group-containing monomer include ordinary hydroxyl group-containing monomers such as hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxypropyl methacrylate. Further, as the monomer copolymerizable with the hydroxyl group-containing monomer, a monomer generally used in the synthesis of acrylic resin for paints can be widely used, and examples thereof include acrylic acid or methacrylic acid ester of C _1-18 monohydric alcohol, styrene, acrylonitrile, Examples thereof include acrylamide, methacrylamide, N-methylol acrylamide butyl ether and the like.

The acrylic polyol can be obtained, for example, by refining a radical polymerization product obtained by copolymerizing the above-mentioned monomers by heating under reduced pressure or fractional precipitation.

Among the above acrylic polyols, for example, 25 parts by weight of n-butyl methacrylate, 35 parts by weight of n-butyl acrylate and 40 parts by weight of 2-hydroxyethyl acrylate, mercaptan as a chain transfer agent, and azobisisobutyro Acrylic polyols that are purified by copolymerization in a solution using nitrile as a polymerization initiator, followed by decompression treatment and fractionation treatment can be mentioned.

Furthermore, in the present invention, the hydroxyl value of the entire component (A) is 150 to 400.
It is preferable to adjust to mgKOH / g, particularly 210 to 350 mgKOH / g. When the hydroxyl value becomes smaller than 150 mg KOH / g,
Insufficient cross-linking and curing reaction points with component (C) lead to insufficient improvement of scratch resistance. On the other hand, when it exceeds 400 mgKOH / g, water resistance decreases, cissing resistance during coating decreases, and finish appearance decreases. Negative effects such as, for example, appear, which are not preferable. Here, the hydroxyl value (mgKOH / g) indicates the amount of hydroxyl groups in the component, and is a value obtained by converting the equivalent of hydroxyl groups in 1 g (solid content) of the component into mg of KOH. The component (A) preferably has two or more primary hydroxyl groups in one molecule, and more preferably 2.5 to 4.0.

The component (B) is a polyester resin having a weight average molecular weight of 2000 to 50,000, a hydroxyl value of 50 to 200 mgKOH / g, and a cyclohexylene ring content of 7% by weight or more in the resin.

Such a polyester resin is produced by subjecting a polybasic acid and a polyhydric alcohol as main components and subjecting them to a condensation reaction.

As the raw material for producing the polyester resin, any of the raw materials used for producing the low molecular weight polyester polyol of the type (i) of the component (A) can be used.

Examples of the raw material used for introducing the cyclohexylene ring into the resin include hexahydro (anhydrous) phthalic acid, hexahydroisophthalic acid, hexahydroterephthalic acid,
Cyclohexanedimethanol, cyclohexene oxide, methylhexahydro (anhydrous) phthalic acid, etc. are mentioned. Among these, a polyester resin obtained by using hexahydroterephthalic acid is particularly preferable.

In the present invention, it is important that the cyclohexylene ring content in the polyester resin is in the range of 7% by weight or more.
A uniform structure is formed by the interaction based on the compatibility between the component (A) and the component (B), and at this time, it is considered that the cyclohexylene ring plays an important role in the formation of the uniform structure. . If the cyclohexylene ring content is less than 7% by weight, the scratch resistance of the coating film decreases, which is not preferable. The cyclohexylene ring content is 60% by weight when using a known raw material (for example, hexahydrophthalic anhydride, hexahydroterephthalic acid, hexahydroisophthalic acid, cyclohexanedimethanol, etc.) used for introducing a cyclohexylene ring into a resin. Realization to the extent possible.

The polyester resin has a weight average molecular weight of 2000.
~ 50000, preferably in the range of 2200-30000, the hydroxyl value is 50
It should be in the range of -200 mgKOH / g, preferably 60-150 mgKOH / g.

When the weight average molecular weight of the polyester resin is less than 2000, the durability and acid resistance of the coating film are poor, while when it is more than 50,000, the coating workability is poor and the finished appearance, especially the sharpness is poor. Not preferable. Further, when the hydroxyl value is smaller than 50 mgKOH / g, the crosslinking reaction point with the melamine (C) component is insufficient, which causes a decrease in water resistance and the like, while when it is larger than 200 mgKOH / g,
The total amount of the hydroxyl groups in the component (A) is excessive, which adversely affects the moisture resistance of the coating film, reduces the pigment dispersibility, and deteriorates the finished appearance of the coating film.

Further, it is preferable that the polyester resin has a branched structure from the viewpoint of practical coating film performance and scratch resistance. Therefore, it is desirable that the total amount of the trihydric and / or tetrahydric alcohol is 10 mol% or more based on the total amount of the polyhydric alcohol component in the polyester raw material.

The component (C) is an alkoxymonomeric melamine.

In the present invention, the alkoxymonomeric melamine is an average of 3 methylol groups etherified with a monohydric alcohol having 1 to 5 carbon atoms, such as methanol, n-butanol and isobutanol, per triazine nucleus. And having an average degree of condensation of 2 or less, preferably 1.1 to 1.8,
It also means a low molecular weight melamine in which the proportion of mononuclear bodies is 50% by weight or more. As these melamines, as commercially available products, for example, Cymel 303, Cymel 325, Cymel 327, Cymel 350, Cymel 370 (both manufactured by Mitsui Toatsu Chemical Co., Ltd.), Nikarac MS17, Nikarac MS15 (both manufactured by Sanwa Chemical Co., Ltd.), Resinmin 741 (manufactured by Monsanto), Sumimar M-55 (manufactured by Sumitomo Chemical Co., Ltd.), etc., methyl etherified melamine, Cymel 202, Cymel 235, Cymel 238,
Cymel 254, Cymel 272, Cymel 1130 (all manufactured by Mitsui Toatsu Chemicals, Inc.), Nikarac MX-485, Nikarac MX
-487 [all manufactured by Sanwa Chemical Co., Ltd.], methyl ether / butyl ether mixed etherified melamine such as Regimin 755 [manufactured by Monsanto Co.], and the like. If the average degree of condensation of the melamine is more than 2 or the proportion of the mononuclear body is less than 50% by weight, the elasticity of the crosslinked cured product may become uneven and the scratch resistance may be deteriorated, which is not preferable. . Further, when the average number of etherified methylol groups is less than 3 per triazine nucleus, the self-condensation reaction of melamine is likely to occur during heat curing, so that the elasticity of the crosslinked cured product is also nonuniform and the scratch resistance is low. There is a risk that it will fall.

The composition of the present invention contains the above components (A) to (C) as main components, and the composition ratio of these components is 15 to 60 for the component (A) based on the total weight of the components (A) to (C). % By weight, preferably 20-40% by weight, (B) component 15-60% by weight, preferably 30-50% by weight and (C) component 20-50% by weight,
It is preferably 25 to 40% by weight. 15% by weight of component (A)
When the amount is less, the cross-linking reaction with the component (C) is less, the formation of the cross-linked structure is insufficient, and the scratch resistance is insufficient. On the other hand, when it is more than 60% by weight, the moisture resistance, the chemical resistance and the impact resistance Both of these are not preferable because the properties are deteriorated. When the content of the component (B) is less than 15% by weight, the performance of the coating film other than the scratch resistance required for the top coating composition deteriorates,
On the other hand, when it is more than 60% by weight, the scratch resistance is insufficiently improved, which is not preferable. 20% by weight of component (C)
If it is less, the formation of a network (crosslinked structure) that gives elasticity suitable for scratch resistance is not sufficient, while
If it exceeds 50% by weight, on the contrary, the network becomes too dense and the coating film becomes brittle, and the chemical resistance, particularly the acid resistance is lowered, which is not preferable.

The coating composition of the present invention is preferably obtained by dissolving or dispersing the components (A) to (C) in an organic solvent. The organic solvent is preferably one that can dissolve or disperse the components (A) to (C). Specifically, it is a hydrocarbon system such as hexane, heptane, octane, xylene, or toluene, ethyl acetate, butyl acetate, amyl acetate. , Esters such as ethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, hexyl ether, dioxane, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether,
Ethylene glycol monobutyl ether, ethylene glycol diethyl ether, ether systems such as diethylene glycol monobutyl ether, methyl alcohol, ethanol, isopropanol, butanol, amyl alcohol, 2-ethylhexyl alcohol, alcohol systems such as cyclohexanol, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, Ketone-based compounds such as isophorone, aromatic petroleum solvent-based products such as Cosmo Oil Co., Ltd., trade names Swazol 310, Swazol 1000, and Swazol 1500 can be preferably used.

The coating composition of the present invention may further contain a coating surface modifier, a fluidity modifier, an ultraviolet absorber, a light stabilizer, a curing catalyst and the like, if necessary. Among these, the fluidity modifier will be described more specifically.

Since the component (A) of the composition of the present invention has a low molecular weight, it has a low viscosity, and when the coating composition of the present invention is applied, so-called dripping tends to occur. Therefore, it is preferable to add an appropriate fluidity adjusting agent. Conventionally, as the fluidity adjusting agent, silica-based fine powder, bentonite-based adjusting agent, polyamide-based adjusting agent, crosslinked fine particles produced by aqueous emulsion polymerization, crosslinked fine particles produced by non-aqueous system, etc. are known, but these are When any of them was incorporated into the composition of the present invention, there was a marked tendency to reduce the gloss of the coating film, which was not practical. Among the conventionally proposed fluidity modifiers, the diurea-based ones are most suitable because they can improve the dripping ease of the coating composition of the present invention without lowering the gloss of the coating film. It was confirmed that the diurea-based fluidity modifier suppresses the decrease in gloss of the coating film, particularly in connection with the high hydroxyl value and low molecular weight of the component (A). this is,
Since the component (A) has a low molecular weight, the compatibility with diurea tends to be good, and the diurea has good compatibility with unreacted hydroxyl groups remaining in the three-dimensional network structure of the cured coating film. Conceivable. As the diurea-based fluidity adjusting agent, for example, various types proposed in JP-A-53-67733 can be used. Among these, diurea, which is a reaction product of mono-primary amine and diisocyanate, is preferable.

By adding the diurea, the smoothness of the coating film in the wet state is excellent, and the occurrence of sagging or misalignment can be prevented. It is considered that this is because the hydrogen bond between the molecules of diurea is formed with a time lag after the shearing during spray coating, so that the fluidity and the structural viscosity appear interchangeably.

The diisocyanate used for producing the diurea is aliphatic, aromatic or cycloaliphatic. Preferable examples thereof include hexamethylene-1,6-diisocyanate, hexamethylene-1,6-diisocyanate trimer, isophorone diisocyanate, toluene diisocyanate and the like. Further, the mono primary amine includes mono amine or hydroxy mono amine having 1 to 5 aliphatic carbon atoms, and suitable examples include benzyl amine, propyl amine and tertiary butyl amine.
Hydroxymonoamines such as monoamines having 4 to 4 aliphatic carbon atoms, 2-aminoethanol, 1-aminoethanol, 2-aminopropanol, 3-aminopropanol and the like can be mentioned. The reaction of both components is easily carried out, for example, by reacting the same amount of monoamine as diisocyanate in a suitable resin solution at room temperature.
In this case, the resin solution serves to prevent the diurea crystals from aggregating. It is effective to use this diurea in an amount of 0.1 to 3% by weight, more preferably 0.5 to 1.5% by weight, as an effective amount of the resin solid content of the composition of the present invention.

The coating composition of the present invention is a thermosetting coating, and the coating is preferably performed by air spray, airless spray, electrostatic spray coating, etc., and can be cured under normal baking conditions. Further, it is appropriate that the coating film thickness is a cured film thickness of about 20 to 50 μm.

Effect of the Invention The coating composition of the present invention is particularly excellent in scratch resistance of the coating film formed. Therefore, it is particularly preferable to use a base material that is required to have scratch resistance, for example, as a top coating material for automobile outer panels, furniture, building exterior materials, etc., and especially for automobile outer panels with a dark color finish. The coating composition of the present invention is not only excellent in scratch resistance, but also excellent in water resistance, chemical resistance, impact resistance, weather resistance, finished appearance, ease of coating, and the like. Coating composition.

Examples The present invention will be further clarified below with reference to Examples and Comparative Examples. Unless otherwise specified, "part" and "%"
Means "parts by weight" and "% by weight", respectively.

[1] Preparation of Sample (A) Production Example of Component Production Example 1 (Production of Polyol Solution A) 53.8 parts of cyclohexanedimethanol, 12.8 parts of trimethylolpropane, 44.3 parts of adipic acid, and boiling point of 18 in a flask.
Charge 60 parts of an aromatic petroleum solvent [Swazol-1500 (manufactured by Cosmo Oil Co., Ltd.)] at 0 to 220 ° C and 0.5 part of monobutyltin hydroxide, and carry out the reaction while removing condensed water through a water separator under reflux of the solvent. I did. When the acid value reached 7, the reaction was stopped and concentrated under reduced pressure.

The solid concentration of the obtained solution was 80.0%, the hydroxyl value of the solid was 247, the weight average molecular weight (w) was 1170, and the ratio w / n of the number average molecular weight (n) was 1.3.

Production Example 2 (Production of Polyol Solution B) A flask was charged with 32.0 parts of hexahydrophthalic anhydride, 22.8 parts of adipic acid, and 54.6 parts of neopentyl glycol.
The reaction was allowed to proceed while heating to remove condensed water produced from 160 ° C. to 230 ° C. for 5 hours while raising the temperature through a rectification tower. Then, after maintaining the temperature at 230 ° C for 2 hours, kynylene was added, and the reaction was advanced at 230 ° C under reflux of xylol while removing condensed water through a water separator. When the acid value reached 6, the temperature was maintained. While depressurizing the system. The vacuum was continued until about 5 parts of the mixture of low molecular weight product and unreacted neopentyl glycol was removed. Then, it cooled and added 23.5 parts of cellosolve acetate. The solid content of the obtained solution was 80.1%, the hydroxyl value (solid content) was 176, and the w was 950.
It was w / n = 1.28.

Production Example 3 (Production of Polyol C) 25.0 parts of trimethylolpropane, 25.0 parts of ε-caprolactone and 0.1 part of tetrabutyl titanate were charged in a flask, the temperature was raised to 100 ° C., and the temperature was kept for 1 hour. Then, the temperature was raised to 120 ° C, and ε-caprolactone 5
0.0 part was dropped for 1 hour. Then, the temperature was raised to 180 ° C., and the reaction was continued until there was no change in the refractive index of the reaction product. Then, the system was depressurized to remove a small amount of unreacted substances and low molecular weight substances, and then cooled. The solid content concentration of the obtained product is 100%, the hydroxyl value is 302, the w is 1010, and the w / n is 1.31.
Met.

Production Example 4 (Production of Polyol D) Polyol D was produced in the same manner as in Production Example 3 except that 31.5 parts of neopentyl glycol, 68.5 parts of ε-caprolactone and 0.1 part of tetrabutyl titanate were used as raw materials. The obtained product has a solid content of 100% and a hydroxyl value of 3
30, w was 620 and w / n was 1.20.

Production Example 5 (Production of Polyol E) 70 parts of Swazol-1000 (produced by Cosmo Oil Co., Ltd., aromatic petroleum solvent) was charged into a flask and heated to 150 ° C. 25 parts of n-butyl methacrylate, 35 parts of n-butyl acrylate, 40 parts of 2-hydroxyethyl acrylate
Part, azobisisobutyronitrile (AIBN) 4 parts and n-
A mixture of 3 parts of dodecyl mercaptan was added dropwise over 3 hours. Then, 1 part of AIBN powder was divided into 12 parts and added every 5 minutes. After the last addition of AIBN, the mixture was kept at 150 ° C. for 30 minutes and then cooled. Add xylene to this product and solid content concentration
Diluted to 40%. Methanol, which is a poor solvent, was added at 80 ° C, and the mixture was allowed to cool to 20 ° C as it was. The lower layer separated from the two layers was discarded, and the upper layer was reprecipitated in petroleum ether for purification. The precipitated resin was heated and cooled, and then dissolved in a mixed solvent of xylene / n-butanol = 90/10. The finally obtained acrylic resin solution had a solid content concentration of 60%, a hydroxyl value (solid content) of 185, w of 1850 and w / n of 1.50.

Comparative Production Example 1 (Production of Polyol Solution F) A flask was charged with 60.3 parts of cyclohexadimethanol, 6.4 parts of trimethylolpropane and 44.2 parts of adipic acid,
Heated and stirred. The generated condensate water was removed through a rectification tower and the temperature was raised from 160 ° C to 230 ° C over 3 hours. twenty three
After maintaining at 0 ° C. for 1 hour, xylene was added and the reaction was continued at 230 ° C. under the reflux of xylene by the solvent condensation method. When the acid value reached 7, it was cooled and diluted with Swazol-1500 (Cosmo Oil Co., Ltd., aromatic petroleum solvent) to obtain a solid content concentration of 80.
%. The hydroxyl value of the resin solid content of this product is 210,
The w was 1060 and the w / n was 1.80.

Comparative Production Example 2 (Production of Polyol Solution G) A flask was charged with 52.3 parts of neopentyl glycol, 14.7 parts of phthalic anhydride, 21.8 parts of adipic acid, and 20.7 parts of hexahydrophthalic anhydride. While removing the generated condensed water, the temperature was raised from 160 ° C to 230 ° C over 3 hours, and then maintained at 230 ° C for 1 hour. After that, xylene was added and the reaction was continued by the solvent condensation method. When the acid value reached 4, the system was switched to a reduced pressure system and the reduced pressure was continued at 230 ° C. to remove xylene and low molecular weight substances. Then, it cooled and added cellosolve acetate, and set solid content concentration to 80%. The hydroxyl value of the resin solid content was 132, w was 1170, and w / n was 1.40.

Comparative Production Example 3 (Production of Polyol H) Polyol H was produced in the same manner as in Production Example 3 except that 11.7 parts of pentaerythritol, 88.3 parts of ε-caprolactone and 0.1 part of tetrabutyl titanate were used as raw materials. The product has a solid content of 100% and a hydroxyl value of 18
0 and w were 2300, and w / n was 1.35.

Comparative Production Example 4 (Production of Polyol Solution I) After the radical polymerization reaction was completed, the solvent composition was Swazol-1500 / n in the same manner as in Production Example 5 except that purification was not carried out.
-Butanol = 90/10, a polyol solution I having a solid content concentration of 60% was prepared. The hydroxyl value of solid content is 190 and w is 175
0 and w / n were 1.8.

Synthesis Example of Component (B) Synthesis Example 1 (Production of Polyester Resin Solution J) A flask was charged with 42.0 parts of hexahydroterephthalic acid, 22.1 parts of isophthalic acid, 12.1 parts of trimethylolpropane and 37.3 parts of neopentyl glycol and heated. 160 ° C while removing the generated condensed water to the outside of the system via the rectification tower
It took 3 hours to raise the temperature from 230 ° C to 230 ° C. After maintaining at 230 ℃ for 2 hours, add a small amount of xylene under reflux of xylene.
The reaction was allowed to proceed by a solvent condensation method at 0 ° C., and when the acid value reached 6, cooling was performed. This product was diluted with a mixed solvent of xylene / swazol 1000 = 50/50 so that the solid content concentration was 60% to obtain a polyester resin solution J. The obtained resin (solid content) had a hydroxyl value of 125, w of 4010, and a cyclohexylene ring concentration of 20.0%.

Synthesis Example 2 (Production of Polyester Resin Solution K) As raw materials, 29.2 parts of hexahydroterephthalic acid, 26.2 parts of hexahydrophthalic anhydride, cyclohexanedimethanol
A polyester resin solution K was obtained in the same manner as in Synthesis Example 1 except that 43.5 parts and 10.3 parts of trimethylolpropane were used. The solid content concentration of this product is 60%, the hydroxyl value of resin solid content is 90, w is 5800, and the cyclohexylene ring concentration is 52.6%.
Met.

Synthesis Example 3 (Production of Polyester Resin Solution L) Same as Synthesis Example 1 except that hexahydrophthalic anhydride 15.3 parts, isophthalic acid 43.1 parts, adipic acid 7.6 parts, trimethylolpropane 6.5 parts and neopentyl glycol 40.4 parts are used as raw materials. Then, a polyester resin solution L was produced. The solid content concentration of this product is 60%, the hydroxyl value of resin solid content is 58, w is 6470, and the cyclohexylene ring concentration is
It was 8.2%.

Comparative Synthesis Example 1 (Production of Polyester Resin Solution M) Polyester resin solution was prepared in the same manner as in Synthesis Example 1 except that 53.7 parts of isophthalic acid, 12.3 parts of propane, 37.7 parts of neopentyl glycol and 9.0 parts of hexahydrophthalic anhydride were used as raw materials. M was produced. The solid concentration of this product is
The hydroxyl value of the resin solid content was 60%, the w was 3700, and the cyclohexylene ring concentration was 4.8%.

Comparative Synthesis Example 2 (Production of Polyester Resin Solution N) Synthesis Example 1 except that 29.6 parts of hexahydrophthalic anhydride, 21.1 parts of adipic acid, 5.0 parts of phthalic anhydride, 13.1 parts of trimethylolpropane and 40.4 parts of neopentyl glycol were used as raw materials. A polyester resin solution N was produced in the same manner as in. The solid content concentration of this product was 60%, the hydroxyl value of the resin solid content was 186, w was 1820, and the cyclohexylene ring concentration was 15.8%.

Comparative Synthesis Example 3 (Production of Polyester Resin Solution O) Synthesis Example 1 except that 26.6 parts of hexahydrophthalic anhydride, 18.9 parts of adipic acid, 17.9 parts of phthalic anhydride, 5.9 parts of trimethylolpropane and 40.7 parts of neopentyl glycol were used as raw materials. Then, a polyester resin solution O was produced. The solid content concentration of this product is 60%, the hydroxyl value of the resin solid content is 40, w is 5400, and the cyclohexylene ring concentration is 14.1%.
Met.

Flowability modifier, production of polyol-based diurea Preparation example 1 (production of A-based diurea) The 80% polyol solution A obtained in Production example 1 was placed in a flask.
2.5 parts (90 parts as a solid content) was added, 2.6 parts of n-propylamine and 7.4 parts of hexamethylene diisocyanate were mixed with stirring at room temperature, and the mixture was stirred to form an A-based diurea (polyol / diurea = 90/10 solid content ratio). ) Got.

Preparation Examples 2 to 9 (Production of BI Base Diurea) In Preparation Example 1, except that 112.5 parts of the 80% polyol solution A is used, except that an amount of 90 parts as a solid content of each of the polyol solutions B to I is used. Was obtained in the same manner as in Preparation Example to obtain a polyol-based diurea (polyol / diurea = 90/10) based on each of the polyols B to I.

[Examples and Comparative Examples]

Preparation of coating material: Using the samples obtained in Production Example, Synthesis Example and Preparation Example, coating compositions for topcoat having the compositions shown in Tables 1 and 2 were produced.

Pigment dispersion was performed using a batch type sand mill with the resin of component (B) in the respective paint formulations as the dispersing resin.

The amount of diurea in Tables 1 and 2 means only the amount of diurea in the polyol-based diurea (polyol / diurea = 90/10), and the amount of polyol in the polyol-based diurea is shown in Tables 1 and 2 In the column of (A) component of the table,
It is shown as the sum of the other components (A). Moreover, the compounding amounts in Tables 1 and 2 all indicate the amount of solid content or active ingredient.

Next, on the 0.8 mm thick dull steel sheet that had been subjected to zinc phosphate chemical conversion treatment, an epoxy-based cationic electrodeposition coating was electrodeposited to a dry coating film thickness of approximately 20μ, and baked at 170 ° C for 20 minutes, followed by # 400 Sharpen with sandpaper, wipe with petroleum benzine to degrease,
Next, apply an intermediate coating surfacer for automobiles to a dry coating film of about 25μ
After air-spray coating so that it would be as follows, it was baked at 140 ° C for 30 minutes, then sanded with # 400 sandpaper, drained and dried, and then degreased with petroleum benzine to prepare a test material.

Then, each coating composition shown in Tables 1 and 2 was applied to this material with a mixed solvent of xylol / cellosolve acetate / n-butanol = 40/50/10 for a viscosity of 25 to 35 seconds (Ford Carap # 4/20 ° C). ) Adjusted to 28) -32μ
Air spray gun with Wider W71 (Iwata Paint Co., Ltd. air spray gun)
After setting to room temperature for 1 minute, use an electric hot air stove to set
It was baked and cured at 0 ° C. for 30 minutes.

The results of performance tests on this cured coating film are shown in Tables 3 and 4.

The tests in Tables 3 and 4 were carried out according to the following methods.

(Note 4): Appearance of coating film The appearance of the finish of the coating film was evaluated according to the following criteria from glossiness and fleshiness.

◎: Very good ○: Good Δ: Poor ×: Very bad (Note 5): Measurement of image clarity The image clarity was measured using a JCRI-GGD-166 type Gd system (sold by Nippon Color Research Laboratory). The angle was fixed at 55 ° for measurement.

(Note 6): Scratch resistance After the car with the test coated plate attached to the roof was washed 15 times with a car washing machine, the state of the coated surface of the coated plate was observed. As the car washing machine, "PO20 FWRC" manufactured by Yasui Sangyo Co., Ltd. was used. The evaluation criteria are as follows.

⊚: Almost no scratches were found by visual observation, and passed.

◯: Some scratch marks are found, but the degree is extremely slight.

Δ: Scratch was noticeable by visual observation and failed.

× Eye: Clearly noticeable scratches were visually observed and the test failed.

(Note 7): Impact resistance Using a DuPont impact tester, the firing tip radius is 1/2 inch,
Test with a falling weight of 500g. Shown at the maximum height (5 cm increments) that does not show cracks on the painted surface.

(Note 8): Immerse the test piece in a constant temperature water bath with water resistance of 40 ° C for 240 hours. After taking out, the film with no abnormalities such as gloss and blister of the coating film was rated as ◯.

(Note 9): Gasoline wiping resistance Nisseki Silver Gasoline was moistened with gauze, and a 10 cm length of the coated surface was strongly rubbed 8 reciprocations, and then the coated surface was observed. The case where there was almost no scratch or scratch on the coated surface was rated as ◯.

(Note 10): 0.5 cc of acid resistant 10% sulfuric acid was spotted on the coated surface, left standing at 20 ° C and 75% RH for 48 hours, washed with water, and the coated surface was observed. Those with no abnormalities were rated as ◯.

(Note 11): Weather resistance After a 1200-hour test with a sunshine weather meter, the coated plate was washed with water, and the gloss retention rate (%) at 60 ° gloss was evaluated as follows.

◎: 81% or more ○: 75-80% △: 70-74% ×: 69% or less (Note 12): Sagging limit film thickness Steel plate with a length of 45 cm × a width of 25 cm is subjected to electrodeposition coating and intermediate coating, respectively. After baking, the paint to be tested is applied from the left end to the right end in the longitudinal direction of the steel plate using a spray gun so that the film thickness (on the cured film) continuously changes from 10μ to 60μ. A paper tape (1 inch in width) is attached to the coated steel sheet coated with the intermediate coating in advance at a position ⅓ in the width direction so as to fill the lengthwise direction. After applying the paint to be tested, remove the paper tape. Next, the coated plate was set upright, left for 5 minutes, and then baked and cured as it was, and the maximum film thickness without sagging of the coating was defined as the sagging limit film thickness.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yo Sugimura 4-17-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Kansai Paint Co., Ltd. (72) Inventor Shinji Sugiura 4--17-1, Higashi-Hachiman, Hiratsuka, Kanagawa West Paint Co., Ltd. (72) Inventor Akira Suganuma 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd. (72) Inventor Hiroshi Ito 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd. (72) Inventor Hironori Okayasu 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd. (72) Inventor Sonoko Takechi 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd.

Claims (3)

[Claims] 1. A weight-average molecular weight of (A) is less than 400-2000, and weight-average molecular weight (w) and number-average molecular weight (
n) a low molecular weight polyol component having a ratio w / n of 1.6 or less and a hydroxyl value of 150 to 400 mgKOH / g, and (B) a weight average molecular weight of 2000 to 50,000 and a hydroxyl value of Five
A polyester resin having a cyclohexylene ring content of 7% by weight or more and (C) an alkoxymonomeric melamine, which is 0 to 200 mgKOH / g, and is mixed with the above (A) to (C). Based on the total weight of the components, (A) component is 15 to 60% by weight and (B) component is 15% by weight.
A coating composition for a topcoat, characterized in that the content is from 60 to 60% by weight and the component (C) is from 20 to 50% by weight. 2. The composition according to claim 1, wherein at least 10 mol% of the total polyhydric alcohol component constituting the polyester resin as the component (B) is a trihydric alcohol and / or a tetrahydric alcohol. . 3. The composition according to claim 1, wherein 50% by weight or more of the cyclohexylene ring in the polyester resin as the component (B) is based on hexahydroterephthalic acid.