JPH11228904A - High solid top coat and its coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating composition composed of a polyol and a melamine resin, to increase the weight ratio of solids in the coating to reduce the amount of solvent discharged, to improve the weather resistance and the weather resistance. A coating composition having excellent coating properties such as chipping properties and a balanced internal stress is obtained. SOLUTION: An acrylic polyol as a main resin,
A base coat paint composition comprising an amino resin curing agent, a glitter pigment or a color pigment, and a non-aqueous liquid dispersion medium, wherein the acrylic polyol has a hydroxyl value of 40 to 1
A graft portion (C) having a hydroxyl group at a position 1 to 9 atoms away from the acrylic polyol main chain in the acrylic polyol;
A graft portion (D) having a hydroxyl group at a position separated from 0 to 40 atoms by a ratio of 70/30 in terms of a hydroxyl value.
ア ミ ノ 0/100, and the amino resin curing agent has an Mw of 20
00 to 5000 and 500 to 1500.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high solid overcoat film in which the amount of a solvent in the paint is reduced when coating an automobile body, and a method of coating the same. More specifically, the present invention relates to a topcoat paint composition which is excellent in performance such as weather resistance and chipping resistance, balances internal stress, and reduces the amount of solvent discharged during coating, and a coating method therefor.

[0002]

2. Description of the Related Art Conventionally, a base coat paint used as a top coat paint for an automobile body generally has a solid content of 15 to 20% by weight so as to obtain a finished appearance after coating and a predetermined coating film performance. The remaining 85 to 80% by weight is designed to be a solvent. In these paints, in order to improve the coating properties such as weather resistance and chipping resistance, simply increasing the solid content by reducing the amount of solvent used increases the paint viscosity at the time of painting. As a result, a problem arises in atomization at the time of painting. In addition, the flow property after the paint adheres to the object to be coated cannot be ensured, which causes a problem such as a yuzu skin as a paint appearance. Therefore, when increasing the solids content in the paint, it is necessary to reduce the molecular weight of the resin in the paint and to lower the viscosity of the resin itself in order to secure the proper paint viscosity at the time of painting. Painting has been carried out so as not to cause a problem in the flowability after the paint or the paint adheres to the object to be coated.

[0003]

However, lowering the viscosity of the resin itself in the coating reduces the physical properties of the coating when the coating is hardened, and also impairs the coating performance such as weather resistance and chipping resistance. There was a problem of becoming sufficient. Generally, in order to cure a resin having a low molecular weight and obtain a coating performance equivalent to that of a resin having a high molecular weight, it is necessary to increase the bridge structure inside the resin of the coating. However, the reaction between the polyol and the melamine resin used as the base coat paint resin is a dehydration condensation reaction, so that when the reaction amount of both increases, the dehydration amount also increases, and as a result,
Internal stress is generated due to the volume shrinkage of the resin, and depending on the magnitude of the stress, it affects coating film performance.

Accordingly, in a base coat paint composed of a polyol and a melamine resin, the weight ratio of the solid content in the paint is increased to reduce the amount of solvent discharged, to improve the weather resistance,
It has been an issue to obtain a top coat (base coat and clear coat as two coats and one bake coat) having excellent coating performance such as chipping resistance and balanced internal stress.

[0005] The present invention provides a base coat paint which increases the solid content in the base coat paint, is excellent in coating film performance, and has a balanced internal stress, and also provides an excellent coating method.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has been achieved by the present invention having the following construction. That is, the present invention is a base coat paint composition comprising an acrylic polyol as a main resin, an amino resin curing agent, a glitter pigment or a color pigment, and a non-aqueous liquid dispersion medium, wherein the acrylic polyol has a hydroxyl value of 40. ~ 12
0, a graft portion (C) having a hydroxyl group at a position 1 to 9 atoms away from the acrylic polyol main chain in the acrylic polyol, and 10% from the acrylic polyol main chain.
A graft portion (D) having a hydroxyl group at a position separated by 40 atoms, and the ratio of the graft portion (C) to the graft portion (D) is 70/30 to 0/100 in a hydroxyl value ratio.
And the amino resin curing agent is a melamine resin (E) having a weight average molecular weight in the range of 2,000 to 5,000.
And a melamine resin (F) having a weight average molecular weight in the range of 500 to 1500, and the ratio of the melamine resin (E) to the melamine resin (F) is such that the melamine resin (E) / melamine resin (F) The ratio is in the range of 50/50 to 85/15.

The present invention further provides a high-solid topcoat composition comprising the basecoat composition and the following group: (a) an acrylic polyol / amino resin, (b) a chemically blocked acid-type curing agent. Resin containing an epoxy group, and (c) a polyol containing a fluorine atom and a chemically blocked acid and a polyol containing an epoxy group as a main resin, and an amino resin and a polyisocyanate compound or a polyisocyanate compound as a curing agent. Fluorine atom and chemically blocked acid-containing polyol using block / epoxy group-containing polyol /
It comprises a curable clearcoat coating composition comprising a melamine resin / polyisocyanate system.

Further, the method for coating a top coat according to the present invention comprises:
Applying the base coat coating composition to an object to be coated, and then applying a wet-on-wet curable clear coat coating composition comprising a polyol / melamine system in which a polyol is used as a main resin and cured with an amino resin, followed by heat curing. It is characterized by.

Further, the method for coating a high solid overcoating film of the present invention is characterized in that the base coat coating composition is coated on a substrate to be coated with a chemically blocked acid-type curing agent and a resin containing an epoxy group. It is characterized in that the curable clear coat coating composition comprising the combination is applied wet-on-wet, and then cured by heating.

Further, the method for coating a high solid overcoat film according to the present invention is characterized in that the base coat coating composition is coated on an object to be coated, and a polyol containing a fluorine atom and a chemically blocked acid and an epoxy group are added. Polyurethane containing fluorinated and chemically blocked acid / polyepoxy group-containing polyols, melamine resins, and polyisocyanates containing an amino resin and a polyisocyanate compound or a block body thereof as a curing agent, with a polyol containing as a main resin. It is characterized in that the curable clear coat paint composition is applied wet-on-wet and then cured by heating.

Further, the base coat coating film of the present invention is a base coat coating film obtained by applying the above-mentioned base coat coating composition to an object to be coated and then curing by heating, wherein the internal stress of the base coat coating film is 0 to 0. 34.0 kg / cm ²
And the solid content of the base coat paint composition is 30 to 40% by weight when diluted with the paint.

Further, the high solid overcoating film of the present invention is obtained by applying the above base coat coating composition to an object to be coated,
Next, a high solid overcoat obtained by applying a clear coat coating composition and then curing by heating, wherein the internal stress of the base coat is 0 to 34.0 kg /
cm ² , and the solid content of the base coat paint composition is 30 to 40% by weight at the time of paint dilution.

In the present invention, the clear coating composition comprises:
The following group: (a) acrylic polyol / amino resin,
(B) a resin containing a chemically blocked acid-type curing agent and an epoxy group, and (c) a polyol containing a fluorine atom and a chemically blocked acid and a polyol containing an epoxy group as a main resin, and curing. The agent is appropriately selected from an amino resin and a polyisocyanate compound, or a fluorine atom and a chemically blocked acid-containing polyol / epoxy group-containing polyol / melamine resin / polyisocyanate system using a block of a polyisocyanate compound.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The base coat coating composition (A) constituting the top coating composition of the present invention contains an acrylic polyol as a main component and a melamine resin as a curing agent. That is, the composition has an acrylic polyol as a main resin and contains an acrylic polyol having a hydroxyl value in the range of 40 to 120, and has a hydroxyl group at a position 1 to 9 atoms away from the acrylic polyol main chain in the acrylic polyol. 10 to 40 from the graft portion (C) and the acrylic polyol main chain
A graft portion (D) having a hydroxyl group at a position distant from the atom is included. Further, as a melamine resin as an amino resin curing agent, a melamine resin (E) having a weight average molecular weight in the range of 2000 to 5000, and a melamine resin having a weight average molecular weight of 500
Melamine resin (F) in the range of ~ 1500. Hereinafter, these components will be described.

The acrylic polyol has a graft portion (C) and a graft portion (D). The graft portion (C) and the graft portion (D) are contained in one acrylic polyol at a hydroxyl value ratio of: 70 / 30-0 / 10
The ratio of the acrylic polyol containing only the grafted portion (C) to the acrylic polyol containing only the grafted portion (D), even if it is contained at a ratio of 0, is such that the grafted portion (C) / grafted portion (D) You may mix in the ratio of 70 / 30-0 / 100.

The graft portion (C) is composed of 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (Meth) acrylates and the like,
The hydroxyl group-containing acrylic monomer having 1 to 9 atoms from the vinyl group to the hydroxyl group can be contained in the acrylic polyol by a method such as copolymerization with another acrylic monomer.

The graft part (D) is made of Daicel Chemical Industries, Ltd., trade names FM-1, FM-2, FM-3, F-3
M4, FA-1, FA-2, FA-3, FA-4, etc. copolymerize a hydroxyl group-containing acrylic monomer having 10 to 40 atoms from a vinyl group to a hydroxyl group with another acrylic monomer. Can be included in the acrylic polyol.

In the present invention, two kinds of melamine resins which are amino resin curing agents are used. Melamine resins (E) having a weight average molecular weight in the range of 2,000 to 5,000 are trade names Uban 80S, 20E, 20SB. , 2
0HS, 122, 128, and 220 (all manufactured by Mitsui Petrochemical Industries, Ltd.) and the like. As the melamine resin (F) having a weight average molecular weight in the range of 500 to 1500, trade names Cymel 204, 232, 235, 32
7, 370 (all manufactured by Mitsui Cytec Co., Ltd.) and Super Beckamine L116-70 (manufactured by Dainippon Ink and Chemicals, Inc.).

In the base coat coating composition of the present invention, a glitter pigment or a coloring pigment is preferably used.
Here, the brilliant pigment is a pigment exhibiting brilliancy such as metallic luster after completion of a coating film, and refers to, for example, aluminum flake, mica flake, etc., for example, aluminum pace (manufactured by Showa Aluminum Co., Ltd., table name (SAP561)). -PS), etc. As a material for forming the base coat coating composition, a rheology modifier, an ultraviolet absorber,
An appropriate amount of the surface conditioner can be appropriately used.

The base coating material described above is dissolved in an organic solvent. As the organic solvent, a solvent generally used in the production of a paint, for example, an aliphatic hydrogenated compound, an aromatic hydrocarbon, an ether, an ester, or the like can be appropriately used.

Next, the reason for the numerical limitation of the present invention will be described. That is, the base coat paint composition of the present invention, a top coat composition containing this composition, a method of applying these paint compositions, and a base coat film and a high solid top coat film obtained by applying the paint composition. The reason that the acrylic resin having a hydroxyl value in the range of 40 to 120 is contained as the main resin is that when the hydroxyl value is less than 40, the internal crosslinking of the base coat coating composition becomes insufficient, and the coating film properties such as chipping resistance and the like are obtained. Becomes inferior. When the hydroxyl value exceeds 120, the internal stress of the base coat coating composition increases, and the chipping resistance and the accelerated weather resistance deteriorate. A graft portion (C) having a hydroxyl group at a position 1 to 9 atoms away from the acrylic polyol main chain;
A graft portion (D) having a hydroxyl group at a position distant from an atom is contained, and the ratio of the graft portion (C) / graft portion (D) is 70/30 to 0/100 in terms of the hydroxyl value. The graft portion (C) in which the distance of the hydroxyl group from the main chain is less than 9 atoms tends to increase the internal stress inside the base coat, but can be added in an appropriate amount from the viewpoint of economy. Further, the graft portion (D) is effective for suppressing an increase in internal stress and obtaining good coating film properties. When the graft portion (D) has a hydroxyl group at a position closer than 10 atoms from the acrylic polyol main chain,
The internal stress inside the base coat increases, and the coating film properties such as chipping resistance tend to be inferior. When the graft portion (D) has a hydroxyl group at a position more than 40 atoms away from the main chain of the acrylic polyol, the internal crosslinking of the base coat becomes poor, and the coating film properties such as chipping resistance are inferior. Further, when the graft ratio exceeds 70/30, the internal stress inside the base coat exceeds 34.0 kg / cm ² , so that the chipping resistance and the accelerated weather resistance are inferior.

The melamine resin as the amino resin curing agent in the base coat coating composition has a weight average molecular weight of 2,000 to 2,000.
It contains a melamine resin (E) in the range of 5000 and a melamine resin (F) having a weight average molecular weight in the range of 500 to 1500, and the ratio of the melamine resin (E) and the melamine resin (F) is E) / melamine resin (F) are mixed in a weight ratio of 50/50 to 85/15. The melamine resin (E) is effective for suppressing internal stress and obtaining good coating film properties. Also, the melamine resin (F) is effective in improving the solid content during coating. When the weight average molecular weight of the melamine resin (E) is in the range of 2,000 to 5,000, the effect of suppressing the internal stress is insufficient when the weight average molecular weight is less than 2,000, and when the weight average molecular weight is more than 5,000, the melamine resin (E) cannot be used for coating. Solid content is not sufficiently improved. Further, a melamine resin (F) having a weight average molecular weight in the range of 500 to 1500 is used. When the weight average molecular weight is less than 500, the internal stress of the base coat film becomes large, and the chipping resistance and the accelerated weather resistance are deteriorated. If the weight average molecular weight exceeds 1500, the solid content during coating is not sufficiently improved. Melamine resin (E) /
Melamine resin (F) is 50/50 to 85/1 by weight.
The reason for mixing in the range of 5 is that the melamine resin weight ratio is 50
/ 50, the internal stress inside the base coat is 3
Since it exceeds 4.0 kg / cm ² , chipping resistance and accelerated weather resistance are inferior.

In the base coat film and high solid top coat film of the present invention, the internal stress of the base coat film is 0 to 34.0 kg / cm ² . The reason why the internal stress inside the base coat film is 0 to 34.0 kg / cm ² is to secure chipping resistance and accelerated weather resistance. The reason that the solid content of the base coat paint composition is limited to 30 to 40% by weight at the time of coating dilution is that if the solid content of the base coat paint composition is less than 30% by weight at the time of coating dilution, the solvent at the time of coating, which is the gist of the present invention, is used. The effect of reducing emissions is not sufficient. On the other hand, if it exceeds 40% by weight, the atomization performance of the coating material is reduced, and a good coating appearance cannot be obtained.
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

[0024]

Examples and Comparative Examples Next, the present invention will be described more specifically with reference to Examples and Comparative Examples. (Production Example 1) Production of acrylic polyol (C-1) In a four-necked flask equipped with a thermometer, a reflux condenser, a stirrer, and a dropping funnel, 25.0 parts by weight of xylene was initially charged as a solvent initially charged, and stirred. Heat with 140
C. Next, at a temperature of 140 ° C., a mixture of the monomer and the weight initiator having the composition shown in Table 1 (dropping component) was dropped at a constant speed from the dropping funnel over 2 hours. After the completion of dropping, 110
C. for 1 hour, a weight initiator solution (additional catalyst) was added, and when the temperature was further maintained at 110 ° C. for 2 hours, the reaction was terminated, and an acrylic polyol (C-1) having the properties shown in Table 1 was obtained. I got

[0025]

[Table 1]

(Production Example 2) Acrylic polyol (D-
Preparation of 1) 25.0 parts by weight of xylene was initially charged as a solvent in a four-necked flask equipped with a thermometer, a reflux condenser, a stirrer, and a dropping funnel, and heated under stirring.
C. Next, at a temperature of 140 ° C., a mixture of the monomer and the weight initiator having the composition shown in Table 2 (dropping component) was dropped at a constant speed from the dropping funnel over 2 hours. After the completion of dropping, 110
C. for 1 hour, a weight initiator solution (additional catalyst) was added, and the reaction was terminated when the temperature was further maintained at 110 ° C. for 2 hours. The acrylic polyol (D-1) having the properties shown in Table 2 I got

[0027]

[Table 2]

(Production Example 3) Production of Base Coat Coating Composition The composition materials shown in Table 3 were weighed into a container and sufficiently stirred to obtain base coating compositions used in Examples 1 to 6 and Comparative Examples 1 to 7, respectively. Obtained. Examples 1 to 6 and Comparative Examples 1 to 7 An epoxy resin-based cationic electrodeposition paint was applied to a chemical conversion-treated dull steel plate at 20 μm and cured at 170 ° C. for 20 minutes. Product name,
Nippon Oil & Fats Co., Ltd.) was applied to a dry coating film to a thickness of 35 μm, and cured at 140 ° C. for 20 minutes to obtain an object to be coated.
Next, TR-15 (trade name, manufactured by NOF CORPORATION) was added as a diluting solvent to the base coat coating composition shown in Table 3 to adjust the temperature to 13 seconds (20 ° C.) with Fodocup # 4 except for Comparative Example 7. Diluted. (Comparative Example 7 was adjusted so as to have a coating solid content of 30%. The coating viscosity at this time was 14.5 seconds.) These base coat coating compositions were applied by air spray coating on the above-mentioned substrates (drying). Film thickness: 13 μm). 3
After leaving for minutes, the following clear coat paints (B1-B
3) was applied by air spray coating so that the dry film thickness became 35 μm. After standing at room temperature for 10 minutes,
Cured for 1 minute and Examples 1-6 and Comparative Examples 1 respectively
Thus, a finished coating film of No. 7 (that is, a high solid top coating film) was obtained. The obtained finished coating films were subjected to the following coating film performance tests. The internal stress of the base coat film was measured separately by the method described below.

(Clear Coating B1) Basecoat No. 6200 Clear (trade name, manufactured by NOF Corporation) Clear coating composed of acrylic polyol / amino resin

(Clear Coating B2) Froshine No. 1000 Clear (trade name, manufactured by NOF Corporation) A clear coating composed of a chemically blocked acid-type curing agent and a resin containing an epoxy group.

(Clear Paint B3) Froshine F3 Clear (trade name, Nippon Yushi Co., Ltd.)
Clear paint consisting of a fluorine atom and chemically blocked acid-containing polyol / epoxy group-containing polyol / melamine resin / polyisocyanate system

(Test Method for Coating Film Performance) (1) Measurement of Internal Stress After coating the base coat paint composition on tin foil,
After curing at 20 ° C. for 20 minutes, the film is peeled from the tin foil to obtain a free film. This is TM made by Shimadzu Corporation
Using A-50, a film with a test length of 3 mm x 10 mm
It was set at 0 ° C., and the shrinkage stress when this was cooled to room temperature was measured, and this was defined as the internal stress. The internal stress is calculated from the following formula: internal stress (kg / cm ² ) = shrinkage stress (kg) / cross-sectional area of test coating film (cm ² ) (2) Chipping resistance According to ASTM-D-3170 Then, the chipping resistance test was evaluated as follows. (1) Test equipment: QGR Gravelometer (QP
(2) Chip material; marble grain with diameter of about 10 to 15 mm (3) Quantity of chip material; about 250 pieces (4) Blowing air pressure; about 4.8 kg / cm ² (5) Test temperature; C. The periphery of the test plate was covered with a piece of adhesive tape except for the central portion of 40 mm × 40 mm and attached to the test plate holder.
The chip material was jetted at a pressure of cm ² , and the average peeled area caused by the collision was recorded. This average peeled area was 0.3 (m
m ² ) or less was accepted, and 0.3 (mm ² ) or more was unacceptable.

(3) Accelerated weathering resistance JIS D0205 2.2.1 Accelerated weathering resistance test (3) Cracking of the coating film after 2000 hours test was observed with an ultraviolet fluorescent lamp type weathering resistance tester.

(4) Coating Appearance The coating appearance was visually evaluated. Table 3 shows the evaluation results.

[0035]

[Table 3]

[0036]

As described above, the base coat composition, the hybrid top coat composition, the method for applying the hybrid top coat, the base coat and the high solid top coat of the present invention are constituted as described above. Therefore, the effect of increasing the weight ratio of the solid matter in the coating composition to reduce the amount of solvent discharged during coating is exhibited. At the same time, a good coating appearance is obtained, and a coating film having extremely excellent coating properties such as weather resistance and chipping resistance is obtained. Therefore, the coating composition of the present invention is extremely useful as a top coat for automobiles.

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C09D 163/00 C09D 163/00 175/00 175/00 // C08F 290/04 C08F 290/04 (72) Inventor Toshihiko Sada Yokohama, Kanagawa Nissan Motor Co., Ltd. (72) Inventor Takashi Arakawa 2 Takaracho, Kanagawa-ku, Kanagawa-ku, Nissan Motor Co., Ltd.

Claims (7)

[Claims] An acrylic polyol as a main resin,
An amino resin curing agent, a brilliant pigment or a coloring pigment, and a base coat coating composition comprising an organic solvent, wherein the acrylic polyol has a hydroxyl value of 40 to 120, and the acrylic polyol has an acrylic polyol main chain in the acrylic polyol. A graft portion (C) having a hydroxyl group at a position 1 to 9 atoms apart, and 10 to 4
Graft portion having hydroxyl group at position 0 atom away (D)
Wherein the ratio of the graft portion (C) to the graft portion (D) is 70/30 to 0/100 in terms of a hydroxyl value.
The amino resin curing agent has a weight average molecular weight of 2,000 to 50.
Melamine resin (E) having a weight average molecular weight of 500 to 1500 and melamine resin (F) having a weight average molecular weight of 500 to 1500.
Melamine resin (E) and melamine resin (F)
Wherein the weight ratio of melamine resin (E) / melamine resin (F) is in the range of 50/50 to 85/15. 2. A curable clear coat paint composition comprising a polyol / melamine resin system in which a base material is coated with a polyol as a main resin and cured with an amino resin. A method for coating a high solid top coat, characterized by coating on-wet and then heating and curing. 3. A curable clearcoat paint composition comprising a combination of a chemically blocked acid-type hardener and a resin containing an epoxy group, which is obtained by applying the basecoat paint composition of claim 1 to a substrate. A method for coating a high-solid topcoat film, comprising applying the composition on a wet-on-wet basis and then heating and curing. 4. An object to be coated is coated with the base coat coating composition of claim 1, wherein a polyol containing an fluorine group and a chemically blocked acid and a polyol containing an epoxy group are used as a main resin, and a curing agent is used as a curing agent. A method for coating a high solid overcoat film, comprising applying a curable clear coat coating composition using an amino resin and a block body of a polyisocyanate compound or a polyisocyanate compound in a wet-on-wet manner, and then heating and curing the composition. . 5. A base coat paint film obtained by applying the base coat paint composition according to claim 1 to an object to be coated, followed by heat curing, wherein the internal stress of the base coat paint film is 0 to 34.0 kg / cm. ^{2. The} base coat paint film according to 2, wherein the solid content of the base coat paint composition is 30 to 40% by weight when the paint is diluted. 6. A high solid overcoat film obtained by applying the base coat coating composition according to claim 1 to an object to be coated, then applying a clear coat coating composition, and then curing by heating. The internal stress of the film is 0
The high solid overcoat film, wherein the high solids top coat is 34.0 kg / cm ² , and the solid content of the base coat paint composition is 30 to 40% by weight when the paint is diluted. 7. The composition according to claim 1, wherein the clear coating composition comprises:
(A) an acrylic polyol / amino resin, (b) a resin containing a chemically blocked acid-type curing agent and an epoxy group,
And (c) a polyol containing a fluorine atom and a chemically blocked acid and a polyol containing an epoxy group as a main resin, and using an amino resin and a polyisocyanate compound or a block of a polyisocyanate compound as a curing agent. Item 7. A high solid overcoat film according to item 6.