JPS63314281A - Thick-film undercoating composition - Google Patents

Abstract

PURPOSE:To provide the title compsn. which gives a thick film, without occurrence of sags or skim, by one coating, which comprises a particular resin component having an oil length increased by the use of a (semi-)drying oil etc., a microgel and a pigment in predetermined wt. proportions. CONSTITUTION:A resin component which comprises at least one member selected from a phenol resin, a bisphenol-type epoxy resin and an alkyd resin and has an oil length adjusted to 30-55% by the use of a (semi-)drying oil, a (semi-)drying oil fatty acid or esters thereof is used as a main component of a vehicle. 100pts.wt. resin component, 0.5-20pts.wt. microgel and 100-350pts. wt. pigment are compounded together, thereby obtaining the desired thick-film undercoating compsn. A pref. example of the microgel is a particulate crosslinked polymer having a particle size of 0.01-20mum obtd. by emulsion copolymn. of methyl acrylate with ethylene glycol diacrylate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an undercoat composition that can form a thick film with one coating without causing blurring or wrinkling, and particularly relates to an undercoat composition that can form a thick film with one coating without causing blurring or wrinkles, and in particular, This invention relates to a thick-film type undercoat paint composition that does not cause blurring even when coated in a thick film of 80 μm or more and does not cause wrinkles even when heated and dried after coating.

[Conventional technology]

When applying a high-quality finish to metal industrial products such as general machinery, home appliances, heavy electrical equipment, medical/barber equipment, fixtures, sewing machines, switchboards, elevators, etc., the metal surface is usually chemically treated and then a primer coat is applied. Depending on the situation, an intermediate coat is applied and then a top coat is applied.

In this case, since the surface smoothness of cast products is particularly low, it is necessary to make the undercoat sufficiently thick in order to obtain a high-quality finish.

Despite the large number of requests for thick coating,
If a thick film is applied all at once, the resin that makes up the paint will become less viscous during heating and drying, causing blurring. If a solvent with a fast evaporation rate is used as a diluent (thinner) to prevent blurring, the surface of the paint film will dry earlier, and the solvent remaining inside the paint film during heating and drying will be released due to the condensation reaction of the structural resin. The water penetrates the paint film and causes pinholes. For this reason, thick film coating causes sagging and pinholes (underarms).
It was an extremely difficult task to satisfy both of these requirements at the same time.

Due to these circumstances, currently in the field of thick film finishing, which requires a total coating film of 70 to 80 μm or more, one coat is applied at a thickness of about 20 to 30 μm, and several coats are used to apply the undercoat and intermediate coat. Combine painting and topcoating as appropriate,
For example, the reality is that it takes three coats, heat-dries three times (referred to as "three coats, three bakes"), or more than that to complete the finish.

Therefore, various proposals have been made regarding coating compositions that can form thick coating films without causing sag or pinholes.

JP-A No. 53-133233 discloses that a film-forming polyester resin, a volatile organic solvent, and fine polymer particles that are insoluble and stably dispersed in the polyester resin and the organic solvent are applied by spraying, and then an organic A method of painting by evaporating the solvent is disclosed. This coating method can be used for both top coating and undercoating.

Furthermore, JP-A No. 60-210673 discloses an alkyd resin having an oil length of 25% or less and a number average molecular weight of 1000 to 5000;
A thick film type paint comprising a vehicle comprising an acrylic resin with a number average molecular weight of 10,000 to 30,000 and a microgel, and a vehicle in which the microgel is 0.5 to 20 parts per 100 parts of the alkyd resin and the acrylic resin. A composition is disclosed.

[Problem that the invention seeks to solve]

However, the above-mentioned JP-A-53-133233 and 6
When the coating compositions disclosed in any of No. 0-210673 are used as an undercoat, they form a thick film to the extent necessary to obtain sufficient smoothness without causing sagging or pinholes in one coating. It turns out that it is not possible to do this.

Therefore, an object of the present invention is to provide a composition for an undercoat paint that can form a film as thick as necessary to obtain sufficient smoothness without causing sag or pinholes in one application. be.

[Means for solving problems]

As a result of intensive research in view of the above objectives, the present inventors have found that by controlling the oil length of the resin component of the vehicle and adding a predetermined amount of microgel, it is possible to coat the film in a thick film of about 60 to 80 μm or more. The inventors discovered that it is possible to obtain an undercoat composition that does not cause sag or pinholes, and came up with the present invention.

That is, the thick-film type undercoat composition of the present invention contains phenolic resin, bisphenol, and the like, in which the oil length is 30 to 55% using a drying oil, a drying oil fatty acid, a semi-drying oil, a semi-drying oil fatty acid, or an esterified product thereof. The main component of the vehicle is a resin component consisting of one or more of type epoxy resins and alkyd resins, and contains 0.5 to 20 parts by weight of microgel and 100 to 350 parts by weight of pigment per 100 parts by weight of the resin component. It is characterized by

The characteristics of the undercoat composition of the present invention are that (1) a so-called medium oil ester type resin is used and (2) microgel is added in a highly concentrated pigment system in order to improve the sag limit film thickness. . The above (1) and (2) are also effective as countermeasures against pinholes during heat drying, which allows (3) to use solvents with medium to high boiling points, and (4) to improve the composition of solvents. (5) It is also possible to reduce the dependence on melamine curing, thereby suppressing the occurrence of pinholes.

The features (1) to (5) will be explained in detail below.

A short oil ester resin with an oil length of less than 30% is usually used as an undercoat vehicle for industrial coatings that are dried by heating.
Because the resin has a high viscosity and is poorly soluble, a large amount of diluent (thinner) is required to achieve a viscosity suitable for painting, resulting in low heating residue (NV) during painting, making it difficult to apply thick films. .

In the present invention, by using a so-called medium oil ester type resin with an oil length of 30 to 55%, the resin face has a low viscosity and is easily soluble in solvents. , thick film coating properties have been improved. In addition, by using microgel, the structural viscosity of the paint was maintained even after thinner dilution, and thick film coating properties were significantly improved.

Furthermore, as the sag resistance has been significantly improved through the use of microgels, there is less need to rely on early volatilization of solvents, making it possible to use medium to high boiling point solvents. Furthermore, as mentioned above, since the amount of solvent blended can be reduced, the critical underarm film thickness during heat drying is improved. Furthermore, by lowering the dependence on melamine curing, early curing of the coating film surface can be prevented, and from this point of view as well, the critical underarm film thickness can be improved.

The vehicle resin used in the undercoat composition of the present invention is a phenolic resin or bisphenol type resin in which the oil length is 30 to 50% using a drying oil, a drying oil fatty acid, a semi-drying oil, a semi-drying oil fatty acid, or an esterified product thereof. Consists of one or more of epoxy resin and alkyd resin.

Phenol resin is a resin obtained by condensation of phenols and formaldehyde, and can be used alone or for modifying alkyd resins.

The number average molecular weight is preferably about 2,000 to 5,000.

Bisphenol-type epoxy resin is a resin having an epoxy group at the end, and is typically obtained by condensation of bisphenol A and epichlorohydrin.

The number average molecular weight is preferably about 1000 to 3000.

Alkyd resin is a type of polyester resin obtained by condensation of polyhydric alcohol and polybasic acid.

As polyhydric alcohols, ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol polypropylene glycol, neopentyl glycol, 1,2-11,8-
12.3- or 1,4-butanediol, 1.5-bentanediol, 1.6-hexanediol, hydrogenated bisphenol A, hydroxyalkylated bisphenol A
, 1,4-cyclohexane dimetatool, 2,2-dimethyl-3-hydroxypropyl-2,2-dimethyl-3
-Hydroxypropione-), 2.2.4-)dimethyl-1,3-pentanediol, N,N-bis-(2-
(hydroxyethyl) dimethylhydantoin, polytetramethylene ether glycol, polycaprolactone polyol, glycerin, sorbitol, trimethylolethane, trimethylolpropane, trimethylolbutane, hexanetriol, pentaerythritol, dipentaerythritol, tris-(hydroxyethyl) incyanate, etc. One or more of these can be used in combination.

In addition, as polybasic acids, phthalic acid, phthalic anhydride, tetrahydrophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, methyltetrahydrophthalic acid, methyltetrahydrophthalic anhydride,
Himic anhydride, trimellitic acid, trimellitic anhydride, pyromellitic acid, pyromellitic anhydride, isophthalic acid, terephthalic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, adipic acid, azelaic acid, sebacic acid, Succinic acid, succinic anhydride, lactic acid, dodecenyl succinic acid, dodecenyl succinic anhydride, cyclohexane-1,
One or more types of 4-dicarboxylic acids, endoacid anhydrides, etc. can be used in combination.

These resins are made using drying oils, drying oil fatty acids, semi-drying oils, semi-drying oil fatty acids, or esterified products thereof.
Denature to 0 to 55%. These oil components include linseed oil, tung oil, dehydrated castor oil, soybean oil, safflower oil, tall oil, or fatty acids or esterified products thereof. Non-drying oils are difficult to dry at room temperature. Furthermore, if the oil length of these resins is less than 30%, not only will drying at room temperature by oxidative polymerization become difficult, but the resulting coating film will become too hard and have poor impact resistance. On the other hand, oil length is 55
If it exceeds %, drying will be slow and baking hardening will not be possible.

The microgel used in the present invention is disclosed in Japanese Patent Application Laid-Open No. 61-42579.
As disclosed in the above issue, an emulsion polymerization of an ethylenically unsaturated monomer and a crosslinkable comonomer is carried out in an aqueous medium by a known method to create an emulsion containing crosslinked polymer fine particles, and the powder is spray-dried. Alternatively, a dispersion obtained by replacing water in the emulsion with a solvent is used. Emulsion polymerization can be carried out using known emulsifiers and/or dispersants, but it is preferable to use emulsifiers having zwitterionic groups. This is because when microgels are added to a coating composition, the structural viscosity varies depending on the particle size, so it is important to have a uniform particle size. However, by using an emulsifier with a zwitterionic group, microgels with a uniform particle size can be created. This is because it is easy to obtain.

Ethylenically unsaturated monomers that can be used for the production of microgels include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate,
Isobutyl (meth)acrylate, (meth)acrylic acid 2
- alkyl esters of acrylic acid or methacrylic acid such as ethylhexyl, and other monomers having ethylenically unsaturated bonds that can be copolymerized therewith, such as styrene, α-methylstyrene, vinyltoluene, t-butylstyrene,
Ethylene, propylene, nyl acetate, vinyl propionate, acrylonitrile, methacrylate trile, (meth)
Examples include dimethylaminoethyl acrylate. Two or more types of these monomers may be used.

Examples of crosslinkable copolymerizable monomers include monomers having two or more radically polymerizable ethylenically unsaturated bonds in the molecule, and monomers containing two types of ethylenically unsaturated groups that can react with each other. There is a mass.

Monomers having two or more radically polymerizable ethylenically unsaturated groups in the molecule include polymerizable unsaturated monocarboxylic acid esters of polyhydric alcohols, polymerizable unsaturated alcohol esters of polybasic acids, and These include aromatic compounds substituted with one or more vinyl groups, such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, and triethylene glycol dimethacrylate. Methylolpropane triacrylate, 1,4-phthanediol diacrylate, neopentyl glycol diacrylate,
1.6-hexanediol diacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, glycerol dimethacrylate, glycerol allyloxy dimethacrylate) , 1.1
．． 1-) Lishydroxymethylethane diacrylate, 1.1.1-trishydroxymethylethane triacrylate, 1,1.1-)lishydroxymethylethane dimethacrylate, 1,1.1-trishydroxymethylethane trimethacrylate, 1,1.1-trishydroxymethylpropanediac, relay), 1.1.1
-trishydroxymethylpropane triacrylate),
1.1.1-) Lishydroxymethylethane dimethacrylate, 1.1.1-Trishydroxymethylpropane trimethacrylate, triallyl cyanurate, triallyl isocyanurate, triallyl trimellitate, diallyl terephthalate, diallyl phthalate and divinyl Benzene etc. are al.

Furthermore, as a monomer for crosslinking purposes, two types of ethylenically unsaturated groups that can react with each other are used instead of or together with a monomer having two or more radically polymerizable ethylenically unsaturated groups in the molecule. It is also possible to use monomers containing For example, glycidyl group-containing ethylenically unsaturated monomers such as glycidyl methacrylate and glycidyl acrylate; carboxyl group-containing ethylenically unsaturated monomers such as acrylic acid, methacrylic acid, and crotonic acid; 2-hydroxyethyl acrylate, hydroxypropyl acrylate, Hydroxyl group-containing ethylenically unsaturated monomers such as 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, allyl alcohol, methalyl alcohol; and vinyl isocyanate,
Examples include ethylenically unsaturated monomers having an isocyanate group such as impropenyl isocyanate. However, in addition to these, any combination of two ethylenically unsaturated monomers each carrying a group capable of reacting with each other can be used.

The particle size of the microgels ranges from 0.01 to 10 μm colloidal size, preferably from 0.02 to 5 μm.

The amount of microgel added is 0 per 100 parts by weight of the resin component.
．． It is 5 to 20 parts by weight. If it is less than 0.5 parts by weight, the effect of preventing creases will be insufficient, and if it exceeds 20 parts by weight, the smoothness of the coating will decrease. The preferred amount of microgel is 1.0 to 10 times the amount of repellent.

The coating composition of the present invention can be used as an undercoat using coloring pigments such as titanium oxide, carbon black, red iron, chromate-based pigments, etc.
Contains antirust pigments such as phosphate pigments, and extender pigments such as calcium carbonate, clay, and talc. The total amount of these pigments is
The amount is in the range of 100 to 350 parts by weight based on 100 parts by weight of the resin solid content. If the total amount of pigment is less than 100 parts by weight, the heating residue during coating is reduced, resulting in poor film thickness and poor polishability as an undercoat. On the other hand, if it exceeds 350 parts by weight, the adhesion to metal will decrease.

The coating composition of the present invention may also contain a curing agent. Examples of the curing agent include melamine resins such as n-butylated melamine resin and isobutylated melamine resin, and benzoguanamine resin.

These resins are usually produced by adding or condensing an amino compound such as melamine or benzoguanamine with an aldehyde such as formaldehyde or paraformaldehyde.
Next, it is obtained by etherification with a monohydric alcohol having 1 to 4 carbon atoms.

The amount of the curing agent is 15 parts by weight or less based on 100 parts by weight of the total amount of the resin component. If more than 15 parts by weight of the curing agent is contained, crosslinking of the coating film will proceed too much, and pinholes will likely occur due to evaporation of water produced by the condensation reaction of the solvent and structural resin. By reducing the amount of curing agent in this way, the pinhole (armpit) limit film thickness can be reduced to 40~
It has improved by 50 μm.

An organic solvent with a relatively high boiling point can be used in the coating composition of the present invention. This is because the use of microgel significantly improves the sagging properties, so there is no need to make it highly volatile. For this reason, the underarm film thickness limit during heat drying is set to 30
It can be improved by as much as ~40 μm. Examples of such organic solvents include xylene, toluene, and the like. The amount of solvent to be blended is such that the coating viscosity of the resulting paint is approximately 80 to 200 seconds/No., 4 Ford cups (25° C.).

Furthermore, various additives such as viscosity modifiers such as organic bentonite, polymeric amide compounds, and polyoxy compounds, surface modifiers such as silicone resins and fluorocarbon resins, and metal salt drying agents may be added to the coating composition of the present invention. amount can be blended.

Next, a coating method using the thick film type undercoat composition of the present invention will be explained. Although the coating composition of the present invention can be used in normal temperature drying lines, it is especially effective when used in baking lines. Therefore, the case where it is used in a baking line will be explained.

First, the metal surface to be coated is chemically treated with phosphate to form a phosphate film with a thickness of about 3 to 8 μm. Drying is 8
It is carried out for 6 to 10 minutes at 0 to 100°C. Next, using the coating composition of the present invention, an undercoat with a film thickness of about 50 to 100 μm is formed by one or multiple (but two) coatings. The coating is preferably carried out by spraying or electrostatic coating. 110-1
Bake at 30° C. for 15-20 minutes. After that, if necessary, apply putty to a film thickness of 50 to 100 μm using polyester putty, etc., and after drying for 6 to 14 hours or more, #18
Wet-sand with 0-220 waterproof paper. Furthermore, if necessary, use the same paint composition as the undercoat to achieve a film thickness of 50 to 10.
Form an intermediate coating of 0 μm and heat at 110 to 130 °C for 15
Dry for ~20 minutes.

Finally, apply a melamine resin top coat to a film thickness of 30 to 4
Form a 0 μm overcoat. Apply this top coat to 110-13
Bake by heating at 0°C for 15-20 minutes.

[For production]

Since the undercoat composition of the present invention contains an alkyd resin modified with a drying oil or semi-drying oil to have an oil length of 30 to 55% as the main component of the vehicle, it has low viscosity and is easily soluble in solvents. Therefore, the amount of solvent can be reduced,
Even if the film is thicker, armpits are less likely to occur. In addition, it has oxidative polymerizability, and if a curing agent such as melamine resin is not used, or even if it is used, the amount blended is small, so that the degree of dependence on melamine curing is low.

Therefore, there is a good balance between the curing of the coating film and the evaporation of water generated by the solvent and condensation reaction, and the critical film thickness under the armpit is 40 to 5.
It has improved by 0 μm. Furthermore, add 0.5 to 2 microgels.
By containing 0 parts by weight, the structural viscosity of the coating film is improved,
Sagging can be effectively prevented.

〔Example〕

The present invention will be explained in more detail by the following examples.
The present invention is not limited thereto.

Example of microgel production: 134 parts by weight of bishydroxyethyl taurine and 1 part of neopentyl glycol were added to a 2β Kolben equipped with a stirrer, a nitrogen inlet tube, a temperature control device, a condenser, and a decanter.
30 parts by weight of azelaic acid, 236 parts by weight of azelaic acid, 186 parts by weight of phthalic anhydride, and 27 parts by weight of xylene were charged, the temperature was raised, and the water produced by the reaction was azeotropically removed with xylene. The temperature was raised to 190°C over about 2 hours from the start of refluxing, stirring and dehydration were continued until the acid value equivalent to carboxylic acid reached 145, and then the mixture was cooled to 140°C. then 1
The temperature was maintained at 40 °C, and the temperature was maintained at 40 °C.
Part by weight was added dropwise over 30 minutes, and stirring was continued for 2 hours.
The reaction has ended. The obtained polyester resin has an acid value of 59
, hydroxyl number 90, Mn 1054.

Then, after stirring, the capacity 1β equipped with a cooler and temperature control device
Into a reaction vessel were placed 232 parts by weight of deionized water, 10 parts by weight of the above polyester resin, and 0.0 parts by weight of dimethylethanolamine.
75 parts by weight were charged and dissolved while stirring while maintaining the temperature at 80°C, and to this was added 4.5 parts by weight of azobiscyanovaleric acid, 45 parts by weight of deionized water, and 4.5 parts by weight of dimethylethanolamine.
A solution dissolved in 3 parts by weight was added. Next, 70.7 parts by weight of methyl methacrylate, 94 parts by weight of n-butyl acrylate
．． 2 parts by weight of styrene, 70.7 parts by weight of styrene, 30 parts by weight of 2-hydroxyethyl acrylate, and 4.5 parts by weight of ethylene glycol dimethacrylate.
It took several minutes to drip. After the dropwise addition, 1.5 parts by weight of azobiscyanovaleric acid dissolved in 15 parts by weight of deionized water and 1.4 parts by weight of dimethylethanolamine was further added, and stirring was continued at 80° C. for 60 minutes. In this way, the non-volatile content is 45% by weight, the pH is 7.2), the viscosity is 92 cps (25
An emulsion was obtained. This emulsion was spray dried to obtain a microgel. The average particle size was 0.8 μm.

Example 1 Tall oil fatty acid modified epoxy resin face with oil length of 40% (
Resin solid content 50% by weight, xylene 50% by weight, IET-
4 (trade name) manufactured by Nippon Paint ■), 10 parts by weight of zinc chromate rust-inhibiting pigment, 10 parts by weight of red iron oxide, 20 parts by weight of calcium carbonate, 10 parts by weight of talc, and a zinc naphthenate desiccant. 0.1 part by weight and xylene 10
The above-mentioned microgel was added to the resulting mixture in the amount shown in Table 1 below, and finally the mixture was mixed with xylene so that the coating viscosity was approximately 60 seconds/No., 4 Ford Cups (25°C). It was diluted to obtain an undercoat paint composition.

Each paint composition thus obtained was applied to Wider #7.
1 Using a spray gun (manufactured by Iwata Painting Equipment ■), gradient coating was applied to a vertically suspended 45 cm K 30 cm steel plate (having 10 holes of 5 mm diameter) so that the dry film thickness was 30 to 150 μm. The paint film was observed with the naked eye 30 minutes after painting, and the thickness of the thickest part around the hole where no sag occurred was determined as the sag limit film thickness. Then 2 at 130 °C
Baking was performed for 0 minutes, and the surface smoothness, presence or absence of pinholes, hardness, and impact resistance of the resulting coating film were measured. The results are shown in Table 1.

Notes to Table 1 = (1) ◎: Extremely good smoothness O: Good smoothness ∆: Slightly uneven ×: Significant unevenness (2) ◎: Not at all ○: Not at all △: Partly × : Available on the entire surface (3) Pencil hardness (4) JIS K 54006.138 method weight 500
g As is clear from the results with an impact punch of 172 inches or more, the amount of microgel is 0.
When the amount is in the range of 5 to 20 parts by weight, a thick undercoat film with no sagging or pinholes, a smooth surface, and excellent mechanical strength can be obtained.

Example 2 An esterified product of a phenol-modified alkyd resin with an oil length of 45% using linseed oil fatty acids (Betsukosol #1 (trade name), Dainippon Ink@!ri) 20% by weight of Red Garla as a pigment, Zinc chromate 20% by weight, calcium carbonate 40% by weight and talc 20% by weight
100 parts by weight, 200 parts by weight, and 350 parts by weight of mixtures consisting of the following were added, respectively. Further, for each sample, samples were prepared in which the microgel was not added and 3 parts by weight were added to 100 parts by weight of the resin solid content. The composition of each sample is shown in Table 2.

For each sample, the sag limit film thickness was measured in the same manner as in Example 1. Furthermore, after baking each at 130 °C for 20 minutes, the smoothness of the resulting coating film, the presence or absence of pinholes,
Hardness and impact resistance were measured. The measurement results are also shown in Table 2.

As is clear from the above results, for pigments, 100
A satisfactory coating film can be obtained at 350 parts by weight, but it can be seen that when no microgel is added, the sag limit film thickness is small and the thick film coating properties are poor. On the other hand, when 3 parts by weight of microgel is blended, the sag limit film thickness is as large as 60 μm or more, indicating excellent thick film coating properties and also excellent smoothness with no pinholes. .

Comparative Example 1 Same as Example 2 except that in Samples No. 7.9 and 11 of Example 2, a phenol-modified alkyd resin ester with an oil length of 20% was used instead of a phenol-modified alkyd resin ester with an oil length of 45%. The sag limit film thickness, smoothness, pinholes, hardness, and impact resistance were measured using the same method.

The results are shown in Table 3.

Table 3 Note: (1) to (4) Same as Table 1.

From the above results, it can be seen that when the oil length is as small as 20%, the sag limit film thickness is significantly smaller than that of the paint with the corresponding composition (sample No. 7.9.11), and there are many pinholes.

〔Effect of the invention〕

As detailed above, the thick film type primer coating composition of the present invention has a medium oil ester resin with a high oil length of 30 to 55% as the main component of the vehicle, so it can be coated with a high coating viscosity. The amount of diluent can be lower. Therefore, it is possible to effectively prevent sagging when the film is thickened, and also to reduce the occurrence of pinholes (flanks) due to solvent vaporization. Furthermore, since it contains microgel, the structural viscosity becomes high, and it is possible to prevent sagging due to thickening of the film. Furthermore, by increasing the amount of pigment blended, the film thickness and polishability as an undercoat are improved.

The basecoat composition of the present invention also provides a thick basecoat with good smoothness, hardness and impact resistance, so that a topcoat can be applied thereon to provide a higher acid coating. Further, due to such thick film coating properties, when the undercoat composition of the present invention is used, the productivity of coating is greatly improved.

Claims (2)

[Claims] (1) Using drying oil, drying oil fatty acid, semi-drying oil, semi-drying oil fatty acid, or esterified products thereof, the oil length is adjusted to 30 to 55.
The main component of the vehicle is a resin component consisting of one or more of phenol resin, bisphenol type epoxy resin, and alkyd resin, and 0.5 to 20 parts by weight of microgel and 100 parts by weight of microgel per 100 parts by weight of the resin component. ~
A thick film type undercoat composition characterized by containing 350 parts by weight. (2) In the thick film type undercoat composition according to claim 1, the microgel has a particle size of 0.01 to 10.
A thick-film type undercoat paint composition characterized by comprising microparticles of a crosslinked polymer having a diameter of μm, insoluble in the vehicle and solvent, and uniformly dispersed in the paint composition.