JPH06136294A - Chipping-resistant coating composition - Google Patents

Abstract

PURPOSE:To provide the coating composition containing an aqueous emulsion component as a main material, preventing the sudden scattering of water contained even when heated after coated, and not producing bubbles even when coated into thick coating films. CONSTITUTION:The coating composition comprises as a main material an aqueous emulsion resin which can thermally be dried and cured after coated, and the starch of water-absorbing polymer and/or the silica of water-retaining filler which absorb and hold water in the aqueous emulsion resin and gradually release the absorbed water when heated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chipping-resistant coating applied to the back and bottom surfaces of automobiles for rust prevention, or a chipping-resistant coating used for a sealing agent filled in gaps such as joints and joints of steel plates. A coating composition for
In particular, it relates to a chipping-resistant coating composition containing an aqueous emulsion-based component as a main material.

[0002]

2. Description of the Related Art A chipping-resistant coating composition of this type is
It is applied to the back of the car floor, the bottom of the gasoline tank, etc.
Prevents rust from occurring due to flaws such as flying stones. Conventionally, the chipping-resistant coating composition,
Primarily vinyl chloride organosols are used. However, the anti-chipping coating composition made of vinyl chloride organosol generates harmful gases such as dioxins when the vehicle is discarded. Therefore, in recent years, there has been a demand for a chipping-resistant coating composition using a material other than vinyl chloride.

As a means for solving this problem, a chipping-resistant coating composition containing an aqueous emulsion resin as a main component has been developed and applied to the bottom surface of a gasoline tank or the like.

A technique relating to an emulsion-based coating composition for chipping resistance is disclosed in, for example, JP-A-2-2826.
No. 9 and Japanese Patent Application Laid-Open No. 4-142375.

[0005]

By the way, in order to prevent the chipping-resistant coating composition applied to the bottom surface of automobiles, the bottom surface of gasoline tanks, etc. from being scratched by flying stones and rusting, It is applied to a thick film of about 2000 μm. However, in the chipping-resistant coating composition in which the main material is an aqueous emulsion resin,
During baking after coating, the moisture inside becomes abruptly bubbled and bumps in a short time, resulting in the formation of armpits. When the armpit occurs, external rainwater and the like easily enter the inside from the surface of the chipping-resistant coating composition, so that rust easily occurs, and although it is in a part that is difficult to see, it is visually Is also not preferable.

Therefore, in the case of parts such as a gasoline tank, after the sol is applied, the setting time is set to be long, for example, it is allowed to stand at room temperature for 20 to 30 hours to gradually release the internal moisture, and then 110 Baking is prevented by baking at a high temperature of 130 ° C or preliminary drying at a relatively low temperature of about 60-80 ° C and then baking at a high temperature of 110-130 ° C. Along with this, the drying equipment is also designed to be able to dry for a long time.

On the other hand, when a coating composition for chipping resistance is applied to the floor back surface of an automobile using an aqueous emulsion resin as a main material, the vehicle body itself is dried and heated. However, long-time drying requires a large space and drying equipment, and a large-scale line needs to be newly installed or modified. For this reason, it is desirable to be able to dry at high temperature immediately after coating, but in that case, as described above, the armpit is generated. For this reason, it has been difficult to apply a thick coating composition for chipping resistance containing an aqueous emulsion resin as a main component to the floor and the back of an automobile.

Therefore, the present invention is a chipping-resistant coating mainly composed of an aqueous emulsion-based component, which prevents abrupt water scattering during heating after coating and does not cause a crack even when coated on a thick film. It is an object to provide a composition.

[0009]

A coating composition for chipping resistance according to the present invention is an aqueous emulsion resin as a main material which is dried and cured by heating after coating, and absorbs and retains water in the aqueous emulsion resin. However, it is blended with a water absorbing agent and / or a water retaining agent that gradually releases upon heating.

Examples of the aqueous emulsion resin include epoxy modified alkyd resin, polyether, acryl, urethane, SBR and the like.

As the water absorbing agent, a water absorbing polymer such as starch represented by the molecular formula of (C ₆ H ₁₀ O ₅ ) _n can be used, and commercially available potato starch can also be used.

As the water retention agent, water retention fillers such as porous silica, sepiolite, clay and bentonite can be used.

The chipping-resistant coating composition also contains other fillers such as talc, calcium carbonate, mica and barium sulfate, color pigments such as carbon black, rust preventive pigments, extender pigments, dispersants and thickeners. Additives such as agents can be added.

The coating of the anti-chipping coating composition on the metal surface of the under floor of an automobile can be carried out by a known coating means such as airless spraying or air spraying.

The sol applied to the metal surface or the like can be made into a cured coating film by setting for a short time and then heating at 110 to 130 ° C. for 30 minutes.

[0016]

In the present invention, the water-absorbing agent and / or the water-retaining agent absorbs water in the aqueous emulsion resin at room temperature, or starts to absorb water when gradually heated to, for example, 60 to 80 ° C. Then, the water absorbing agent and / or the water retaining agent retains the absorbed water inside, and gradually releases the water as the heating temperature rises. This reduces the evaporation rate of water in the water-based emulsion resin,
Since it scatters little by little, no cracking occurs even when the chipping-resistant coating composition is applied thickly. The water-retaining effect can be further enhanced by using the water-absorbing agent and the water-retaining agent together, but even if either one is used alone, the corresponding effect can be obtained.

[0017]

EXAMPLES Examples of the present invention will be described below.

The coating composition for chipping resistance of this Example is
Aqueous emulsion resin (R
X-946, manufactured by Nippon Carbide Co., Ltd., calcium carbonate (heavy calcium carbonate, Takehara Chemical Co., Ltd.), starch as a water-absorbing polymer, silica as a water-retaining filler (Siloiro-244, Fuji Devison Chemical ( Co., Ltd.), a dispersant (Nopcos Perth 44C, San Nopco Co., Ltd.), an antifoaming agent (Formaster H2, San Nopco Co., Ltd.), and a rust preventive pigment (View Sun 11M, Sakai Chemical Industry Co., Ltd.) It was

Here, the starch is represented by the molecular formula of (C ₆ H ₁₀ O ₅ ) _n , and commercially available potato starch and the like can also be used.

The blending ratio is shown in Table 1. The unit of Table 1 is parts by weight.

[0021]

[Table 1]

That is, in Example 1, only starch, which is a water-absorbing polymer, was added as a water-absorbing agent, in Example 2, only silica, which was a water-retaining filler, was added as a water-retaining agent, and in Example 3, a water-absorbing polymer was added. And the silica which is a water-retaining filler are added.

A coating composition for chipping resistance having each of the above formulations was applied to a metal plate by spraying and baked under predetermined conditions to prepare a test panel.

As a comparative example, a test panel containing no water absorbing agent or water retaining agent was also prepared.

Next, the chipping-resistant coating compositions of the respective examples and comparative examples were evaluated. The evaluation items are the side limit film thickness, chipping resistance and adhesion, and the results are shown in Table 2.

[0026]

[Table 2]

Here, the side limit film thickness is gradually changed by gradient coating in which the sol is sequentially thickly applied from one end side to the other end side of the test panel, and after setting, a short time setting, that is, 5 After leaving for 13 minutes,
The film was baked at 0 ° C. for 30 minutes, and the part where the coating film had an armpit was confirmed by visual observation.

The chipping resistance of the sol is 500 μm.
After being applied to a film thickness of m and baked under heating conditions of 130 ° C. for 30 minutes, the test panel is tilted at 60 degrees with respect to the vertical direction and passed through a pipe with a height of 2 m and an inner diameter of 2 cm to obtain JI.
It was evaluated by dropping a nut of S-B1181 type 3 M-4 vertically and measuring the total weight of the nut at the time when the coating film was broken.

For adhesion, a sol is applied to a film thickness of 300 μm, and a test panel baked under heating conditions of 130 ° C. for 30 minutes is used, and a cutter knife is used to make a cross-cut in the shape of eyes at an interval of 1 mm × 1 mm. Was put in, and the tape was attached to the upper surface thereof, and then the tape was rapidly peeled off, and the number of the remaining eyes was counted and evaluated.

In Table 2, in Comparative Examples in which no water-absorbing agent and water-retaining agent were added, the limit film thickness at which no sideways were generated was 50.
Since it is only 0 μm, it is usually difficult to secure a predetermined chipping resistance with this film thickness. On the other hand, in all of the Examples, a film thickness of 1000 μm can be cleared, and in particular, in Example 3 in which the water-absorbing polymer and the water-retaining filler are used together,
A film thickness of 400 μm can be secured, and the highest anti-arming effect is exhibited. From this, it is found that the water-absorbent polymer or the water-retaining filler alone exerts a predetermined effect, and it can be expected that a higher effect can be expected by using them together.

On the other hand, the chipping resistance test and the adhesion test show the same value and good adhesion in both Examples and Comparative Examples, so that the addition of the water absorbing agent and the water retaining agent causes the deterioration of the special performance. It can be said that there is no such thing.

In the above, the reason why the thick film does not cause the armpit is that the water-absorbing agent and the water-retaining agent start absorbing water in the aqueous emulsion resin at 60 to 80 ° C. This is due to the fact that as the temperature rises further, the moisture inside is gradually released and bumping does not occur.

As described above, the coating composition for chipping resistance of the above-mentioned examples absorbs and holds an aqueous emulsion resin as a main material, which is dried and cured by heating after coating, and water in the aqueous emulsion resin, It is a mixture of water-absorbing polymer starch and / or silica, which is a water-retaining filler, which is gradually released by heating.

Therefore, according to the above-mentioned embodiment, the starch and / or silica absorbs the water in the aqueous emulsion resin and retains it inside, and gradually releases the water as the heating temperature rises. For this reason, the water evaporation rate becomes small and the side wall is not generated, so that a thick film is possible and good chipping resistance can be secured. As a result, it is possible to paint and bake under almost the same conditions as the vinyl chloride organosol that has been used conventionally, and the coating dryer for the vinyl chloride organosol can be used as it is, so a large-scale coating is required separately. There is no need to newly install or modify the drying device. Also, there is no need to expand the space for equipment.

By the way, the coating composition for chipping resistance of the present invention can also be used as a sealing agent which does not use a vinyl chloride-based component, for example, is filled in a gap such as a joint or a joint of a steel sheet. .

[0036]

As described above, the coating composition for chipping resistance of the present invention absorbs and retains an aqueous emulsion resin as a main material, which is dried and cured by heating after coating, and water in the aqueous emulsion resin. However, it is blended with a water absorbing agent and / or a water retaining agent that gradually releases upon heating. Therefore, the water-absorbing agent and / or the water-retaining agent absorbs the water in the aqueous emulsion-based resin and retains it inside, and gradually releases the water as the heating temperature rises,
Since the water evaporation rate is low, no armpits will occur. As a result, a thick film can be obtained, and good chipping resistance can be secured.

[Procedure amendment]

[Submission date] April 12, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

As the water absorbing agent, a water absorbing polymer such as starch represented by the molecular formula of (C ₆ H ₁₀ O ₅ ) _n can be used.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

To coat the coating composition for chipping resistance on the electro- deposited surface of the under floor of an automobile, airless spray,
It can be performed by a known coating means such as air spray.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

The sol applied to the electrodeposition-coated surface was set at a temperature of 110 to 130 ° C. for 30 minutes after setting for a short time.
By heating for a minute, a cured coating film can be obtained.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

The coating composition for chipping resistance of this Example is
Aqueous emulsion resin (R
X-946, manufactured by Nippon Carbide Co., Ltd., calcium carbonate (heavy calcium carbonate, Takehara Chemical Co., Ltd.), starch as a water-absorbing polymer, and silica ( SA) as a water-retaining filler.
Iroid-244 , Fuji Davison Chemical Co., Ltd., dispersant (Nopcos Perth 44C, San Nopco Co., Ltd.), antifoaming agent (Formaster H2, San Nopco Co., Ltd.), anti-corrosion pigment (View Sun 11M, Sakai Chemical Industry ( Strain)).

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

Here, starch is represented by the molecular formula of (C ₆ H ₁₀ O ₅ ) _n .

[Procedure correction 6]

[Document name to be amended] Statement

[Name of item to be corrected] 0023

[Correction method] Change

[Correction content]

A coating composition for chipping resistance of each of the above formulations was applied to the electrodeposition coated surface by spraying and baked under predetermined conditions to prepare a test panel.

Claims (1)

[Claims] 1. An aqueous emulsion resin as a main material which is dried and cured by heating after coating, and is mixed with the aqueous emulsion resin, absorbs and retains water in the aqueous emulsion resin, and gradually releases by heating. A coating composition for chipping resistance, comprising a water absorbing agent and / or a water retaining agent.