JPH09241580A - Chipping primer and method for forming chipping-resistant coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chipping primer which possesses excellent coatability, high profitability and can obtain a coating film having good chipping resistance. SOLUTION: This chipping primer comprises: 30 to 79 pts.wt. base resin composed mainly of 25 to 60wt.% straight-chain polyester resin having a hydroxyl group in its both ends, 1 to 8wt.% polyester resin having a sulfonate group in its terminal, 20 to 60wt.% lactone-modified polyester resin, and 10 to 30wt.% epoxy resin; 10 to 50 pts.wt. crosslinking agent; and 1 to 50 pts.wt. pigment containing 1 to 5 pts.wt. basic carbon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an automobile hood,
TECHNICAL FIELD The present invention relates to a primer that constitutes a laminated coating film used in a portion such as a roof that is damaged by stone bounce, particularly a chipping primer having excellent chipping prevention properties, and a method for forming a chipping resistant coating film using the same.

[0002]

2. Description of the Related Art As a tipping primer for automobiles, a tipping primer containing a chlorinated polyethylene resin as a main component has been proposed and generally used. For example, JP-A-61-1147
No. 79 is mainly a modified polyolefin resin (chlorinated polyolefin, etc.) in which a cationic electrodeposition paint is applied to a steel plate, and then the static glass transition temperature of the formed coating film is −30 to −60 ° C. Disclosed is a method for coating a steel sheet, which comprises applying a middle coat paint and a top coat paint after applying a barrier coat as a component. In addition, JP-A-61-118180
JP-A No. 2000-242242 also discloses coating with a barrier coat containing a similar modified polyolefin resin (chlorinated polyolefin, etc.) as a main component. However, the chipping primer containing a chlorinated polyethylene resin as a basic resin has a poor solubility in an organic solvent, so that the solid content during coating is extremely low. Therefore, a large amount of paint is used to obtain a predetermined film thickness. Also, because the solubility of polyethylene resin is poor,
After painting, a large amount of organic solvent is required to wash the painting machine and piping. Further, in recent years, the required quality of chipping resistance has increased, and a chipping primer having a higher degree of chipping resistance has been required. However, a chlorinated polyethylene resin as a basic resin cannot meet this request.

Further, as a chipping primer based on a polyether ester resin-amino resin system,
Japanese Unexamined Patent Publication No. 63-130677 discloses a chipping resistant material which comprises an amino resin and a polyether ester resin containing 1 to 50% by weight of a polyether diol having 5 or more ether bonds in one molecule. A coating composition is proposed. However, this coating composition for chipping resistance has a problem that the recoating coating film is peeled off between the electrodeposition coating film and the chipping resistant coating film by chipping.

With respect to chipping resistance, it is possible to reduce peeling at the coating interface and also to obtain high chipping resistance when the top coat film has a high film thickness, for example, in the case of a recoating film. It is necessary.

Therefore, an object of the present invention is to provide a chipping primer which is excellent in coating workability, economical, and capable of forming a coating film having good chipping resistance.

Another object of the present invention is to provide a coating method capable of forming a coating film having excellent coating workability, high economy, and good chipping resistance.

[0007]

As a result of earnest research in view of the above object, the present inventor has found that the use of a basic resin composed of a plurality of specific polyester resins and epoxy resins and a cross-linking agent makes it possible to obtain a coating excellent in chipping resistance. A chipping primer that gives a film can be obtained, and the solubility in general organic solvents can be improved, so that improvement in coating efficiency and reduction in the amount of solvent used for cleaning coating machines and pipes can be achieved. Electrodeposition coating of primer-
The present invention was discovered by discovering that it can be applied to an intermediate coating-top coating system and an electrodeposition coating-top coating system.

That is, the tipping primer of the present invention has (A) 25 to 60% by weight of a linear polyester resin having hydroxyl groups at both ends (A-1) and a sulfonic acid group at the ends (A-2). 1 to 8% by weight of polyester resin, (A-3) 20 to 60% by weight of lactone-modified polyester resin, and (A-4) epoxy resin
1 to 50 parts by weight of a pigment containing 30 to 79 parts by weight of a basic resin containing 10 to 30% by weight as a main component, (B) 10 to 50 parts by weight of a crosslinking agent, and (C) 1 to 5 parts by weight of basic carbon. A chipping primer characterized by comprising:

The method of the present invention for forming a chipping-resistant coating film using the above-mentioned chipping primer is
The chipping primer of the present invention (1) in electrodeposition coating-intermediate coating-overcoating system between the electrodeposition coating film and the intermediate coating film, or between the intermediate coating film and the top coating film, or (2 ) Electrodeposition coating-overcoating system It is characterized in that it is applied between the electrodeposition coating film and the topcoating film.

Hereinafter, the present invention will be described in detail. [1] Composition of Chipping Primer (A) Basic Resin The basic resin is composed of a plurality of polyester resins and epoxy resins, and the polyester resin is (A-1) a linear polyester resin having hydroxyl groups at both ends, (A-2 ) A polyester resin having a sulfonic acid group at the terminal and (A-3) a lactone-modified polyester resin. These polyester resins are for imparting pigment dispersibility, chipping resistance, and curability. The basic structure of any of the polyester resins is obtained by polycondensation (esterification) of a polyhydric alcohol and a polybasic acid or an anhydride thereof.

As the polyhydric alcohol, ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol,
Polypropylene glycol, neopentyl glycol,
1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, 2,2-Dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxypropionate (BASHPN), 2,2,
4-Trimethyl-1,3-pentanediol, polytetramethylene ether glycol, polycaprolactone polyol, glycerin, sorbitol, annitol, trimethylolpropane, hexanetriol, pentaerythritol, dipentaerythritol and the like, and polyhydric alcohols thereof. Can be used in combination of two or more.

Examples of polybasic acids or anhydrides thereof include phthalic acid, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic acid, methyltetrahydrophthalic anhydride, hymic acid anhydride, and trimellitic acid. 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 , Dodecenyl succinic acid, dodecenyl succinic anhydride and the like, and these can be used in combination of two or more kinds.

(A-1) Polyester Resin Having Hydroxyl Group at Both Ends The polyester resin having hydroxyl groups at both ends is one in which a continuous ester chain is formed by using the polybasic acid and the polyhydric alcohol. , A resin component for imparting a more advanced chipping prevention function. In order to contain hydroxyl groups at both ends, for example, n polybasic acids and n + 1.1
One or more polyhydric alcohols are used. Dibasic acid and dihydric alcohol are preferably used, and more preferably dibasic acid and cyclohexanedimethanol are used. In the present invention, among polyester resins having hydroxyl groups at both ends, those having a hydroxyl value of 100 to 300 are preferable, and those of 200 to 250 are more preferable. The number average molecular weight is 400 to 1,000.
Those of 450 to 470 are more preferable.

The blending ratio of the polyester resin having hydroxyl groups at both ends is 25 to 60% by weight based on 100% by weight of the basic resin.
And If the mixing ratio is less than 25% by weight, the coating film becomes brittle and the chipping resistance is lowered, and if it exceeds 60% by weight, the coating film hardness and water resistance are lowered. It is preferably 30 to 55% by weight.

(A-2) Polyester Resin Having Sulfonic Acid Group at the Terminal The polyester resin having a sulfonic acid group at the terminal is used for controlling the curability of the coating film. has a continuous ester linkage generated using an alcohol, a part of the polyhydric alcohol component, the following general ^{formula: R 1 R 2 R 3 N} -a-SO 3 - ··· (I) ( However, R ¹ is an alkyl group having 1 to 20 carbon atoms having at least one hydroxyl group, R ² and R ³ are hydrogen atoms, an alkyl group having 1 to 20 carbon atoms, or at least one hydroxyl group and / or A linear or cyclic alkyl group having a sulfonic acid group, which may be the same or different, A
Is a linear or branched alkylene group having 1 to 6 carbon atoms, a phenylene group, or a substituted phenylene group. ) And a sulfonic acid group-containing compound. A method for producing such a polyester resin having a sulfonic acid group at the terminal is described in detail in JP-A-56-34725.

In the present invention, among the polyester resins having a sulfonic acid group at the terminal, those having an acid value of 30 to 150 are preferable, and those having an acid value of 40 to 150 are more preferable. Further, those having a number average molecular weight of 500 to 5,000 are preferable, and those having a number average molecular weight of 700 to 3,000 are more preferable.

The compounding ratio of the polyester resin having a terminal sulfonic acid group is 1 to 8% by weight based on 100% by weight of the basic resin.
And If the blending ratio is less than 1% by weight, the curability is insufficient, and if it exceeds 8% by weight, the water resistance is lowered. Preferably it is 1 to 5 parts by weight.

(A-3) Lactone-modified polyester resin The lactone-modified polyester resin modifies a continuous ester chain produced by using the polybasic acid and the polyhydric alcohol with a lactone having 6 to 8 carbon atoms. By
It has improved chipping resistance. The modified amount of the lactone is preferably 5 to 40 parts by weight, and more preferably 10 to 30 parts by weight, based on 100 parts by weight of the polyester resin (based on solid content). As the lactone, ε-caprolactone, ζ-
Enanthlactone, η-caprylolactone, or a ring-substituted product thereof (having a heterocyclic ring-constituting carbon atom with a substituent) or the like is used.

In the present invention, among the lactone-modified polyester resins, those having a hydroxyl value of 50 to 200 are preferred, and 70 to
170 is more preferable. Further, those having an acid value of 2 to 20 are preferable, and those having an acid value of 5 to 15 are more preferable. Furthermore, those having a number average molecular weight of 800 to 4,000 are preferred, and 1500 to 3,
000 is more preferable.

The compounding ratio of the lactone-modified polyester resin is 20 to 60% by weight based on 100% by weight of the basic resin. If the compounding ratio is less than 20% by weight, the dispersibility is lowered, and if it exceeds 60% by weight, the chipping resistance is lowered. Preferably 30
~ 55% by weight.

(A-4) Epoxy resin Epoxy resin is used to provide adhesion. As the epoxy resin, it is preferable to use a bisphenol A type glycidyl epoxy resin, a bisphenol F type glycidyl epoxy resin, or the like.

The mixing ratio of the epoxy resin is 100% of the basic resin.
10 to 30% by weight per weight%. If this blending ratio is less than 10% by weight, the adhesion will be insufficient, and if it exceeds 30% by weight, the water resistance will be reduced. Preferably it is 15 to 25% by weight.

The basic resin (A) containing (A-1) to (A-4) as an essential component is 30 to 79 parts by weight with (A) + (B) + (C) as 100 parts by weight. . If the blending ratio is less than 30 parts by weight, the flexibility of the coating film is reduced, so the chipping resistance is insufficient,
On the other hand, if the amount exceeds 79 parts by weight, the hardness of the coating film decreases and the water resistance and the like becomes insufficient. It is preferably 40 to 65 parts by weight.

(B) Cross-linking agent As the cross-linking agent, one melamine nucleus has an average of 0.5 to 2 imino groups, and the average degree of polymerization of the melamine nucleus is 1.5 to.
A butyl etherified melamine resin of 3.0 is preferred. If the amount of imino groups is less than 0.5, the curability is not sufficient, and if the amount of imino groups exceeds 2.0, the coating film becomes brittle and chipping resistance decreases. Similarly, when the average degree of polymerization exceeds 3.0, the coating film becomes brittle and the chipping resistance is lowered.

The cross-linking agent is 10 to 50 parts by weight based on 100 parts by weight of (A) + (B) + (C). If this blending ratio is less than 10 parts by weight, the crosslink density will be low and the water resistance will be insufficient. If it exceeds 50 parts by weight, the coating film will be brittle and chipping resistance will be insufficient. Preferably it is 20 to 40 parts by weight.

(C) Pigment The pigment used in the present invention contains basic carbon as an essential component. The basic carbon is a solution in which the proportions of pigment, distilled water and ethyl alcohol are 0.8 g, 40 ml and 0.5 ml, respectively, and the pH of the solution is alkaline, preferably 8 to 10, for example, Ketjen Black (Ketjen Black). Black International Co., Ltd.) and the like. When acidic carbon is included, the adhesion with the cationic electrodeposition coating film is reduced, so basic carbon is particularly effective for improving the adhesion.
The reason for this is presumed to be due to electrical interaction with the electrodeposition coating film.

As other pigments, titanium dioxide, cyanine blue, cyanine green, quinacridone, indanthrone, isoindolinone, perylene, anthrapyrimidine, benzimidazolone, yellow iron oxide, red iron oxide and the like may be used as needed. Coloring pigments and extender pigments such as barium sulfate, talc and aluminum silicate can be used.

The blending ratio of the pigment is 1 to 50 parts by weight, with (A) + (B) + (C) being 100 parts by weight. If the mixing ratio exceeds 50 parts by weight, the coating film becomes brittle and the chipping resistance decreases, and if it is less than 1 part by weight, the adhesiveness decreases. The mixing ratio of the basic carbon is 1 to 5 parts by weight with (A) + (B) + (C) being 100 parts by weight. If the amount of basic carbon is less than 1 part by weight, the adhesion will be insufficient, and if it exceeds 5 parts by weight, the pigment dispersibility will be poor.

(D) Other components The chipping primer of the present invention comprises (A) a basic resin, (B)
In addition to the essential components consisting of the cross-linking agent and the (C) pigment, the following thickeners, organic solvents and additives may be contained.

(1) Thickener As the thickener, for example, those obtained by emulsion polymerization using various acrylic monomers disclosed in JP-A-58-129066 as a main component, and disclosed in JP-A-56-90819. Mainly composed of a cross-linked polymer composed of the above-mentioned ethylenically unsaturated monomer, an aqueous microgel emulsion of an acrylic resin cross-linked with a polyfunctional crosslinking agent disclosed in JP-A-56-76447, JP-B-60-27702 Copolymers containing (meth) acrylic acid and (meth) acrylic acid disclosed in JP-A-56-5802, hydroxymethylamino group, alkoxymethylamino group and copolymerization with them. Examples thereof include crosslinkable polymer fine particles having a functional group capable of controlling, organic bentonite, fatty acid polyamide, polyethylene oxide and the like.

(2) Organic solvent As the organic solvent, any organic solvent widely used in paints or a mixture thereof can be used.
For example, aromatic hydrocarbons such as toluene or xylene, n
-Aromatic hydrocarbons such as hexane and heptane, petroleum fractions of various boiling points consisting mainly of aliphatic hydrocarbons and having some aromatic hydrocarbons, butyl acetate, acetylene glycol diacetate, 2-ethoxyethyl acetate, etc. Examples thereof include ester acetates, ketones such as methyl isobutyl ketone, and alcohols such as butyl alcohol.

(3) Additives Additives include conventional acid catalysts, ultraviolet absorbers, surface modifiers, leveling agents, pigment dispersants, plasticizers, defoamers and the like.

[2] Coating Method The tipping primer of the present invention can be used in any of (1) electrodeposition coating-intermediate coating-top coating system, and (2) electrodeposition coating-top coating system. . In the system of (1),
It is applied between the electrodeposition coating film and the intermediate coating film, or between the intermediate coating film and the top coating film, and in the system of (2), it is applied between the electrodeposition coating film and the top coating film. To do.

(1) Electrodeposition coating-intermediate coating-overcoating system When a chipping primer is used between the electrodeposition coating film and the intermediate coating film First, the material to be coated is electrodeposition coated. However, as the electrodeposition paint, either anionic resin type or cationic resin type can be used. In the present invention, the effect is further enhanced when combined with a cationic resin-based electrodeposition coating composition.

As the resin which is the main component of the electrodeposition paint,
(a) Drying oil or liquid rubber such as polybutadiene (having an epoxidized resin as a skeleton in some cases, such as maleated resin, maleated polybutadiene resin and amine epoxidized polybutadiene resin), (b) resinous polyol There are resins having a fatty acid ester as the main skeleton. When the resin for electrodeposition coating is an acidic resin, it is preferably neutralized with a base such as ammonia, amine or inorganic alkali and dissolved or dispersed in water. In the case of a basic resin, it is preferable to neutralize with an acid such as acetic acid, boric acid, phosphoric acid and the like to dissolve or disperse in water.

In the electrodeposition coating composition, a melamine resin, a cross-linking agent such as a blocked polyisocyanate, a pigment, a solvent and the like commonly used additives may be appropriately incorporated. Usually, the electrodeposition coating film is preferably provided so that the film thickness after baking is 10 to 40 μm. Other conditions in the electrodeposition coating may be the same as those in the conventional electrodeposition coating. Incidentally, it is preferable to carry out a usual chemical conversion treatment before this electrodeposition coating.

The chipping primer of the present invention is applied on the electrodeposition coating film. In order to appropriately dissolve the chipping primer of the present invention in a solvent to form a coating material, it is necessary to satisfactorily disperse and mix the components. It includes paint shakers, dissolvers, which are commonly used in the manufacture of paints,
Devices such as a ball mill, a sand grind mill and a kneader can be used.

The tipping primer of the present invention is diluted with a solvent so as to have an appropriate viscosity, and then applied on the electrodeposition coating film by a method such as spraying or coating. The viscosity at the time of coating can be measured using a Ford cup. As the coating machine, an atomizing type coating machine is preferably used, and examples thereof include an air spray coating machine and an air atomizing type or rotary electrostatic coating machine. The thickness of the chipping-resistant coating film is preferably 2 to 20 μm as a dry film thickness. If the thickness of the chipping-resistant coating film is less than 2 μm, the chipping resistance is poor. If the thickness exceeds 20 μm, the upper and lower coating films are mixed during wet-on-wet coating, resulting in poor appearance. More preferable chipping resistance coating thickness is 5 to 15
μm.

Next, intermediate coating is performed. The intermediate coating can be performed on the chipping primer coating film by a wet-on-wet system and / or a preheat system.

As the intermediate coating material, a coating material using an alkyd resin, a polyester resin, an acrylic resin type basic resin and a crosslinking agent such as a melamine resin or a block polyisocyanate can be used. The coating can be performed by a conventional method, for example, electrostatic coating. Baking can also be performed by a conventional method. The film thickness of the intermediate coating film is preferably 20 to 60 μm as a dry film thickness.

As the intermediate coating composition, a "color intermediate coating composition" containing a coloring pigment may be used in order to exhibit design characteristics in combination with the top coating composition. In these resins, the resin system may be any of organic solvent type, water type and powder type.

As the top-coat paint, paints such as acrylic resin paints, polyester resin paints and fluororesin paints can be used. In these resins, the resin system may be any of organic solvent type, water type and powder type. The coating conditions for the top coating may be the same as the specifications for the conventional top coating of automobiles.

When a chipping primer is used between the intermediate coating film and the top coating film: First, electrodeposition coating / baking is performed, then an intermediate coating is applied, and baking is performed. Then, the chipping primer of the present invention is applied onto the intermediate coating film, and top coating is performed by a wet-on-wet method and / or a preheat method.
In this case, the dry film thickness of the chipping primer of the present invention is preferably about 2 to 20 μm. The conditions for the electrodeposition coating, the intermediate coating and the top coating may be the same as those described above.

(2) In the case of electrodeposition coating-overcoating system When a chipping primer is used between the electrodeposition coating film and the overcoating film After the electrodeposition coating is performed in the same manner as described above, the chipping primer of the present invention is used. Apply paint on the electrodeposition coating. The dry film thickness is preferably 5 to 40 μm. Then, in the same manner as above, a top coat paint is applied on the chipping primer coating film.

[0045]

EXAMPLES The present invention will be specifically described by the following production examples, examples and comparative examples, but the present invention is not limited thereto. All parts and amounts are by weight unless otherwise noted.

Production Example 1 of a polyester resin (A-2) having a sulfonic acid group at the terminal
A 2 L Kolben equipped with a production stirrer, a nitrogen introduction tube, a temperature control device, a condenser and a decanter was added to 134 parts of bishydroxyethyl taurine, 130 parts of neopentyl glycol,
236 parts of azelaic acid, 186 parts of phthalic anhydride and xylene
27 parts were charged and the temperature was raised. The water generated by the reaction was removed by azeotropic distillation with xylene. The temperature was raised to 100 ° C over about 2 hours from the start of reflux, and stirring and dehydration were continued until the acid value corresponding to the carboxylic acid reached 145, and then cooled to 140 ° C.
Then, the temperature of 140 ° C was maintained and versic acid glycidyl ester (trade name "CARDURA E10", manufactured by Shell Co.)
314 parts was added dropwise over 30 minutes, and then stirring was continued for 2 hours to complete the reaction. The resulting polyester resin had an acid value of 59, a hydroxyl value of 90, and a number average molecular weight of 1054.

Production Example 2 Production of Lactone-Modified Polyester Resin (A-3) A 2 L Kolben equipped with a stirrer, nitrogen introducing tube, temperature control device, condenser and decanter was placed in 310 parts of trimethylolpropane, 310 parts of neopentyl glycol, And 1,
Charge 188 parts of 6-hexanediol, heat and melt it to 80-100 ° C, start stirring when it becomes possible, and add 707 parts of isophthalic acid and 155 parts of adipic acid to bring the reaction temperature to 180 ° C. The temperature was raised. When water for condensation reaction started to be generated, the temperature was raised to 230 ° C at a uniform rate over 3 hours while distilling water out of the system, and when 230 ° C was reached, the reaction was continued for 2 hours at the same temperature. After that, xylene was added to Kolben and the condensation reaction was continued by refluxing xylene. When the acid value of the resin reached 15.0, the reaction was terminated and cooled. After cooling, 600 parts of xylene was added to produce an oil-free polyester resin varnish. The resulting resin solids have a nonvolatile content of 70.4
%, Acid value 10.4, and hydroxyl value 150.

Take 974 parts of this resin solid content and add ε-
146 parts of caprolactone and 0.4 part of di-n-butyltin dilaurate were added, and the temperature was raised to 150 ° C in a nitrogen atmosphere.
Sequential sampling was performed while maintaining this temperature, and I
The amount of unreacted ε-caprolactone was traced by R, and when the reaction rate reached 98%, the reaction was terminated and cooled. When the temperature in the Kolben became 135 ° C. or lower, 480 parts of xylene was added to obtain a varnish of lactone-modified polyester resin.
The nonvolatile content of this varnish was 70.2%, the acid value of varnish was 9.1, and the hydroxyl value was 130.

Examples 1-6, Comparative Examples 1-2 1. Component of chipping primer (A) Basic resin (A-1) A linear polyester resin having hydroxyl groups at both ends, product name “FLEXOREZ148” (Kusumoto Kasei Co., Ltd.) (A-1) was used. (A-2) Polyester Resin Having Sulfonic Acid Group at Terminal The resin obtained in Production Example 1 was used. (A-3) Lactone-modified polyester resin The resin obtained in Production Example 2 was used. (A-4) Epoxy resin A bisphenol A type glycidyl epoxy resin (trade name "EP-0150" (manufactured by Toto Kasei Co., Ltd.)) (A-4) was used. (A-5) Polyethylene resin Polyethylene resin (trade name "BOR-904", manufactured by Sakai Chemical Industry Co., Ltd.) was used as a basic resin of Comparative Example.

(B) Crosslinking agent A butyl etherified melamine resin (trade name "Uban 20SE-60", manufactured by Mitsui Toatsu Chemicals, Inc.) having a nonvolatile content of 60% was used.

(C) Pigments The pigments shown below were used. (C-1) Basic carbon: Product name "Ketjen Black E
C ”(manufactured by Ketjen Black International). (C-2) Non-basic carbon: Product name“ Carbon MA-100 ”
(Manufactured by Mitsubishi Chemical Corporation). (C-3) Titanium dioxide: trade name "Titanium R-650" (manufactured by Sakai Chemical Co., Ltd.). (C-4) Barium Sulfate: Trade name "Variace B-30" (manufactured by Sakai Chemical Co., Ltd.). (C-5) Talc: Product name "LMR-100" (manufactured by Maruo Calcium Co., Ltd.).

(D) Thickener (D-1) Polyethylene oxide (trade name "Disparon 4200-2
0 "manufactured by Kusumoto Kasei Co., Ltd. (D-2) Crosslinkable polymer fine particles (trade name" AZS-597 "manufactured by Nippon Paint Co., Ltd.).

2. Preparation of chipping primer Basic resin (A), cross-linking agent (B), pigment (C) and, if necessary, thickener (D) are mixed in the composition shown in Table 1, and glass beads are used as a medium. The chipping primer was prepared by putting it in a sand grinder mill and stirring and mixing it uniformly.

3. Evaluation Apply the obtained chipping primer to a tin plate and apply 30
After air-drying at room temperature for minutes, the re-solubility in xylene was measured according to the following criteria, and the paint solubility was evaluated. The results are shown in Table 1. ◯: Melted. ×: Does not dissolve.

Table 1 Examples Comparative Examples Component CP-1 CP-2 CP-3 CP-4 CP-5 CP-6 CP-7 CP-8 (A) Basic resin (A-1) ⁽¹⁾ 21.3 23.2 27.3 27.3 24.6 18.2 23.2− (A-2) ⁽¹⁾ 1.2 1.3 1.5 1.5 1.4 1.5 1.3− (A-3) ⁽¹⁾ 15.5 16.8 18.2 18.2 16.4 27.3 16.8− (A-4) ⁽¹⁾ 11.0 11.9 13.0 13.0 11.6 13.0 11.9− (A-5) ⁽¹⁾ − − − − − − − 57.0 (B) Crosslinking agent ⁽¹⁾ 21.0 26.8 30.0 30.0 36.0 30.0 26.8 38.0 (C) Pigment (C-1) ⁽¹⁾ 5.0 1.0 1.0 1.0 1.0 1.0 − 5.0 (C-2) ⁽¹⁾ − − − − − − 1.0 − (C-3) ⁽¹⁾ 20.0 15.0 6.0 6.0 6.0 6.0 15.0 − (C-4) ⁽¹⁾ 2.5 2.0 1.5 1.5 1.5 1.5 2.0 − (C-5) ⁽¹⁾ 2.5 2.0 1.5 1.5 1.5 1.5 2.0 − (D) Thickener (D-1) ⁽²⁾ 0.04 0.04 0.02 − 0.02 0.02 0.04 − (D-2) ⁽²⁾ − − − 2.0 − − − − Evaluation paint solubility ○ ○ ○ ○ ○ ○ ○ × × (1) Unit: parts by weight. (2) Unit: parts by weight, where (A) + (B) + (C) is 100 parts by weight.

Examples 7-12 and Comparative Examples 3-4 1. Electro-deposition coating and baking SPC-1 dull steel plate is pre-treated with zinc phosphate to produce cationic electro-deposition paint (trade name "Olga U-53", Nippon Paint Co., Ltd.)
17) after coating so that the dry film thickness is about 30 μm.
It was baked at 0 ° C for 30 minutes.

2. Coating and baking of tipping primer and intermediate coating paint Each tipping primer shown in Table 1 is diluted with thinner (ethyl acetate / toluene = 1/1 (weight ratio)) at 17 "/ 20 ° C (#
The viscosity was adjusted so that it would be 3 Ford cups), and painting was performed with an air spray gun. The dry film thickness is from Example 7 to
11 and Comparative Examples 3 to 4 are set to about 10 μm, and Example 6 is set to about 4 μm.
m. Table 2 shows the chipping primer used in each Example and Comparative Example. Set for about 10 minutes after painting,
Next, an intermediate coating (trade name "Olga P-2 Gray", manufactured by Nippon Paint Co., Ltd.) was applied to a dry film thickness of about 35 µm, and baked at 140 ° C for 30 minutes.

3. Topcoat paint and baking Base paint (trade name "Olga TO-H522", manufactured by Nippon Paint Co., Ltd.) is 13 "/ 20 ° C (# 4 Ford cup) with the same thinner used for adjusting the viscosity of the chipping primer.
The viscosity was adjusted so that the dry film thickness was about 17 μm, and coating was performed for 5 minutes. After that, a clear coating (trade name "Olga TO-563 clear" manufactured by Nippon Paint Co., Ltd.) adjusted to 22 "/ 20 ° C (# 4 Ford cup) with the above-mentioned thinner has a dry film thickness of about 35 µm. After painting and setting for 10 minutes, 140 ℃
After baking for 30 minutes, a test piece was obtained.

Further, after the top coating surface of the test piece prepared by the same method as described above is water-polished, the same top coating material is applied twice by the same coating method and baked to give a top coating film having three layers. Got

4. Evaluation of chipping resistance The test pieces (non-coated and coated) of each Example and Comparative Example were kept at -20 ° C, and a gravel meter (manufactured by Suga Test Instruments Co., Ltd., nozzle diameter 15 mm) was used. make use of,
Five 0.75 ± 0.05 g crushed stones were sprayed at an air pressure of 0.55 kgf / cm ² at an angle of 45 °, and the peeled area of the coating film of the test piece was measured.
The chipping resistance was evaluated according to the following criteria. ⊚: Minute peeling (less than 10 mm ² ). ○: less peeling (10 mm ² or more ~25mm less than ^2). △: slightly larger peeling ⁽² or more ~50mm less than ² 25mm). X: Large peeling (50 mm ² or more).

Table 2 Example of chipping resistance No. Chipping Primer No overcoating 2 times Example 7 CP-1 ○ ○ Example 8 CP-2 ◎ ○ Example 9 CP-3 ○ ○ Example 10 CP-4 ○ ○ Example 11 CP-5 ○ ○ Example 12 CP-6 ○ ○ Comparative Example 3 CP-7 △ △ Comparative Example 4 CP-8 ○ △

Examples 13 to 18 and Comparative Examples 5 to 6 The same dull steel sheets used in Example 7 were subjected to electrodeposition coating, baking, intermediate coating and baking in the same manner as in Example 7. Then, in the same manner as in Example 7, each chipping primer shown in Table 1 was applied onto the intermediate coating film to form a chipping-resistant coating film. Examples 13 to 17 and Comparative Examples 5 to 5
No. 6 had a dry film thickness of about 10 μm, and Example 18 had a dry film thickness of about 4 μm. After setting for 2 minutes, a topcoat paint was applied in the same manner as in Example 7 to obtain a test piece. Also, after polishing the top coating surface of the test piece prepared by the same method as above, the same top coating material was applied twice by the same coating method,
By baking, a test piece having a three-layer top coating film was obtained.

The test pieces of each Example and Comparative Example (non-coated and coated) were evaluated for chipping resistance in the same manner as in Example 7. The results are shown in Table 3.

Table 3 Example of chipping resistance No. Chipping Primer No overcoating Overcoating twice Example 13 CP-1 ○ ○ Example 14 CP-2 ○ ○ Example 15 CP-3 ○ ○ Example 16 CP-4 ○ ○ Example 17 CP-5 ○ ○ Example 18 CP-6 ○ ○ Comparative Example 5 CP-7 ○ △ Comparative Example 6 CP-8 ○ △

Examples 19 to 24 and Comparative Examples 7 to 8 The same dull steel sheet used in Example 7 was subjected to electrodeposition coating and baking in the same manner as in Example 7. Then, each chipping primer shown in Table 1 was applied in the same manner as in Example 7 to form a chipping resistant coating film. Example 19-
In 23 and Comparative Examples 7 to 8, the dry film thickness was set to about 10 μm.
No. 24 had a dry film thickness of about 4 μm. After setting for 2 minutes, the top coat paint is applied in the same manner as in Example 7,
A test piece was obtained. Also, after polishing the top coating surface of the test piece prepared by the same method as above, the same top coating material was applied twice by the same coating method and baked to form a top coating film 3 times.
A layered test piece was obtained.

The test pieces of each Example and Comparative Example (non-coated and coated) were evaluated for chipping resistance in the same manner as in Example 7. The results are shown in Table 4.

Table 4 Example of chipping resistance No. Chipping Primer No overcoating Two times overcoating Example 19 CP-1 ○ ○ Example 20 CP-2 ○ ○ Example 21 CP-3 ○ ○ Example 22 CP-4 ○ ○ Example 23 CP-5 ○ ○ Example 24 CP-6 ○ ○ Comparative Example 7 CP-7 ○ △ Comparative Example 8 CP-8 ○ △

As is clear from Tables 2 to 4, the coating films of the examples are excellent in chipping resistance both when the coating is performed and when it is not performed. On the other hand, the coating film of the comparative example is inferior in chipping resistance in either case.

[0069]

As described above in detail, the chipping primer of the present invention can impart excellent chipping resistance to the coating film. Therefore, it is extremely useful as a chipping primer for laminated coating films for automobiles.

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Claims (3)

[Claims] 1. (A) (A-1) 25 to 60% by weight of a linear polyester resin having hydroxyl groups at both ends, and (A-2) 1 to 8% by weight of a polyester resin having a sulfonic acid group at both ends. And (A-
3) 20-60% by weight of lactone-modified polyester resin, (A-
4) A pigment containing 30 to 79 parts by weight of a basic resin containing 10 to 30% by weight of an epoxy resin as a main component, (B) 10 to 50 parts by weight of a crosslinking agent, and (C) 1 to 5 parts by weight of basic carbon. A chipping primer comprising 1 to 50 parts by weight. 2. The chipping primer according to claim 1, wherein the crosslinking agent has an average of 0.5 per melamine nucleus.
It has ~ 2 imino groups and the average degree of polymerization of the melamine nucleus is 1.
A chipping primer which is a butyl etherified melamine resin of 5 to 3. 3. The chipping primer according to claim 1 or 2, (1) in electrodeposition coating-intermediate coating-topcoat coating system, between an electrodeposition coating film and an intermediate coating film, or an intermediate coating film. And (2) an electrodeposition coating-topcoating system, a method for forming a chipping-resistant coating film, characterized by coating between the electrodeposition coating film and the topcoat film.