JPH07166096A - Chipping-resistant coating composition for automobile - Google Patents

Abstract

PURPOSE:To enable a thick film to be formed without developing cracks, blisters, etc., during drying and baking and to enable a reduction in the specific gravity of the film. CONSTITUTION:This composition is an emulsion paint which comprises as a main component an aqueous latex of polymer particles serving as a film-forming ingredient and having an average particles diameter of 0.3mum or larger, and which further contain fine hollow particles as a filler, the latex having a solid content of 50wt.% or higher.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an emulsion-type anti-chipping paint for automobiles, which is applied to a tire house, an underfloor, a front apron, etc. of an automobile to prevent damage to the vehicle due to flying stones.

[0002]

2. Description of the Related Art Conventionally, polyvinyl chloride plastisols have been widely used as coating materials for undercoats of automobiles. Films are often removed by incineration. However, since polyvinyl chloride resin produces hydrogen chloride when incinerated, it is environmentally problematic.

Therefore, a paint that replaces the polyvinyl chloride-based plastisol is desired, and an emulsion-type paint using water as a dispersion medium is drawing attention as a paint in line with this.

However, the emulsion type paint is
There is a problem that it is difficult to form a thick film. That is, when the emulsion type paint is applied thickly, when it is dried by heat (baking), water evaporation due to the drying occurs from the surface, which causes the skin of emulsion particles to be fused on the surface of the coating film. Therefore, there is a problem that the evaporation of water in the undried coating film is hindered, and as a result, the coating film is cracked or swollen. Therefore, while the drying temperature of the vinyl chloride-based plastisol is 140 ° C. for about 30 minutes, the heating rate of the baking furnace is slowed down and the temperature is 70 to 90 ° C. for the purpose of preventing such cracks and swelling. Although the conditions for lowering the furnace temperature to some extent are adopted, such conditions cause a decrease in productivity.

Further, the emulsion-type coating material has a problem that when the amount of the filler is the same as that of the vinyl chloride-based plastisol, the specific gravity of the coating film becomes high, which is contrary to the recent demand for vehicle weight reduction.

The present invention has been made in view of the above circumstances, and provides an emulsion-type anti-chipping coating material for automobiles, which has a low specific gravity in that cracks and swelling are less likely to occur during drying even when a thick film is formed. To aim.

[0007]

Means and Actions for Solving the Problems As a result of intensive studies for achieving the above-mentioned object, the present inventor has found that polymer particles as a coating film component are mainly latex, which is emulsified and dispersed in water as emulsion particles. Emulsion type coating composition having an average particle diameter of 0.3 μm
The solid content of the latex is 50% by weight or more, hollow fine particles are blended as a filler, and an acrylic resin or styrene having a styrene content of 15 to 50% is used as a polymer serving as a coating film component. It has been found that it is effective to use a butadiene-based copolymer resin.

That is, it is conventionally said that the average particle diameter of emulsion particles of latex used as an anti-chipping paint for automobiles is preferably small due to dispersion stability, and emulsion particles having a relatively large particle diameter are preferred. Although it has been said that it is difficult to find out the characteristic, the present inventor uses an emulsion particle having a large average particle size of 0.3 μm or more to achieve high solid differentiation of the aqueous emulsion type coating, It is possible to maintain a low viscosity, so that it is possible to reduce the amount of water that should evaporate in the paint, and since it is easy to volatilize water due to its low viscosity, cracks and swelling during drying can occur even when applied thickly. In addition to being able to prevent the occurrence of thick film, it is possible to significantly prevent the occurrence of swelling of the coating film during drying when hollow fine particles are blended as a filler. In addition to being advantageous for thick film formation, the specific gravity of the coating film can be reduced even when it is thickly coated to more reliably provide chipping resistance. As the type of resin, acrylic resin or styrene content is within 15 to 50%. The inventors have found that the styrene-butadiene-based copolymer resin is suitable, and have completed the present invention.

Therefore, the present invention is an emulsion-type coating material mainly comprising a latex in which polymer particles as coating film components are emulsified and dispersed in water as emulsion particles, and the average particle diameter of the emulsion particles is 0.3 μm or more. And
And, the solid content of the latex is 50% by weight or more, and hollow fine particles are blended as a filler, and a polymer as a coating film component has an acrylic resin or styrene content. 15-50
% Styrene-butadiene copolymer resin is provided for the above-mentioned automotive chipping resistant coating.

The present invention will be described in more detail below. The anti-chipping coating material for automobiles of the present invention mainly comprises a latex in which polymer particles are emulsified and dispersed in water as emulsion particles.

In this case, as such a polymer,
Acrylic resin, styrene-butadiene copolymer resin,
Examples of the urethane resin include acrylic resin and styrene-butadiene copolymer resin from the viewpoints of dispersion stability and storage stability particularly when the solid content is high.
In this case, the styrene-butadiene copolymer resin preferably has a styrene content of 15 to 50%. The average molecular weight of the above resin is preferably high, and specifically, it is preferably 100,000 to 1,000,000 for an acrylic resin and about 50,000 to 200,000 for a styrene-butadiene copolymer resin.

This polymer is used as emulsion particles in latex and has an average particle size of 0.3 μm or more, preferably 0.1.
It is dispersed in a size of about 3 to 0.8 μm. When the average particle size of the polymer particles is smaller than 0.3 μm, the effect of preventing cracks and swelling during drying cannot be sufficiently achieved when a thick film is formed.

The solid content of the latex of the coating material of the present invention is 50% or more, preferably 55% or more. When the solid content is less than 50%, the seizure property is similarly deteriorated and the object of the present invention cannot be achieved.

When obtaining such a latex,
The production method is preferably the hot rubber method.

In the present invention, hollow fine particles are blended in order to reduce the specific gravity of the coating film. Specific examples of such hollow particles include glass balloons, resin balloons, and other balloons.

The glass balloon has an average particle size of 40.
It is preferably about 70 μm and a specific gravity of about 0.4. It should be noted that the paint is 80 to 160 by pressure feeding in the pipe or spray application.
Since pressure is applied mainly to kg / cm ² , generally 120 kg / cm ² , the glass balloon has a pressure resistance of 2
It is preferably 100 kg / cm ² or more. As a commercially available product of such a glass balloon, for example, Cellstar Z-39 manufactured by Asahi Glass Co., Ltd. (average particle diameter 40 μm, specific gravity 0.39,
The pressure resistance is 240 kg / cm ² ).

As the resin balloons, those having an average particle diameter of 40 to 70 μm and a specific gravity of about 0.04 are preferable. Since the paint is baked at 120 to 160 ° C., typically 140 ° C., it is preferable that the resin balloon has heat resistance that does not flatten and melt in this range.
Therefore, as the resin material, vinylidene chloride resin,
Although acrylonitrile resin and other synthetic resins can be mentioned, acrylonitrile resin is most preferable from the viewpoint of heat resistance.

Examples of other balloons include silica balloons, shirasu balloons, carbon inorganic hollow bodies, and the like.

In this case, one of the above-mentioned balloons may be used alone or two or more of them may be used in combination. Specifically, a glass balloon that has good heat resistance while being weak against impact and a resin balloon that lacks heat resistance but is resistant to impact can be blended alone or can be used together, but a resin with a low specific gravity from the viewpoint of cost. It is better to blend the balloon alone.

The content of these hollow fine particles is 0.25 to 60 with respect to 100 parts of the resin component (parts by weight, the same applies hereinafter).
Parts, especially in the range of 0.25 to 30 parts. 0.25
If it is less than 60 parts, it may be difficult to obtain the effect of reducing the specific gravity of the coating film, and if it is more than 60 parts, the performance of the formed coating film may be significantly reduced, and the amount of other fillers added may be small, resulting in high cost. is there.

In addition to the above-mentioned components, the emulsion type coating composition of the present invention may further contain a filler other than hollow fine particles, a defoaming agent, a thickener, a dispersant, a wetting agent and the like, if necessary.

As the filler, for example, calcium carbonate,
Talc, clay, silica, diatomaceous earth, zeolite, magnesium carbonate, mica and the like can be mentioned, but if the shape of the particles of the filler is flat, it tends to hinder the evaporation of water, so among these, the shape of the particles is Non-planar calcium carbonate and diatomaceous earth are preferred. The average particle size of the filler is 1
About 20 μm is preferable.

The amount of the filler compounded is 50 to 300 parts, especially 1 part, per 100 parts of the resin component including the hollow fine particles.
The range of 50 to 250 parts is preferable. If the blending amount is less than 50 parts, appropriate thixotropy may not be obtained even in combination with a thickener, and swelling may occur easily. On the other hand, when it exceeds 300 parts, it becomes difficult for the resin to sufficiently wet the filler, and the coating performance may not be satisfied due to performance degradation, and cracks may easily occur.

The defoaming agent is blended for the purpose of reducing the occurrence of bubbles and facilitating the elimination of bubbles once they are formed, because low viscosity emulsions and emulsion mixtures are likely to cause bubbles by stirring.

The thickening agent is for helping the dispersion of the polymer and the filler to prevent sedimentation, improve the stability of the coating material, finish the resin to an appropriate viscosity, and obtain the balance of both sprayability and thixotropy. For example, one kind of methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, protein, polyvinyl alcohol, sodium acrylate and the like can be used alone or in combination of two or more at a usual dose. The dispersant is for helping the filler to be dispersed in water, and examples thereof include various sodium polyphosphates and surfactants. The amount of the dispersant compounded is preferably higher than usual because the polymer particles used in the present invention have a large particle size.

The anti-chipping paint for automobiles of the present invention can be prepared by mixing the above components.
For example, after the high solid content latex, filler, dispersant, wetting agent, and the like described above are kneaded, a thickener is added to disperse the mixture, and then a defoaming agent is further added to defoam the mixture. The emulsion type coating material of the present invention can be prepared by filtration. In this case, a high-speed disperser is suitable as the disperser, and the kneading and the subsequent viscosity adjustment can be simultaneously performed, so that the production efficiency can be higher than that of other machines.

The chipping-resistant coating material for automobiles of the present invention is used as a coating material for a portion such as an automobile tire house, an underfloor, a front apron, etc. which requires chipping resistance.

In this case, a general high-pressure pump can be used for coating by a spray gun coating method or the like, and the coating amount is 150 to 40 in terms of the thickness of the dried coating material.
It can be about 100 μm.

The drying condition is, for example, 10 to 6 at room temperature.
After leaving it for 0 minutes, it is dried in a calcining furnace at about 110 ° C. for about 8 to 12 minutes, then at 120 to 150 ° C. for 20 to 30 minutes in an intermediate coating furnace, and finally in a top coating furnace at 120 to 150 ° C. for 2 minutes.
Conditions for drying for 0 to 30 minutes can be adopted.

[0030]

EXAMPLES The present invention will be specifically described below by showing Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Example 1, Comparative Example 1] The components shown in Table 1,
Two kinds of emulsion type paints were prepared so that the viscosities were the same, and sprayability, storage stability and baking property were evaluated according to the following methods. The results are also shown in Table 1. <Sprayability> Sample temperature of 20 using airless spray
C, spraying pressure 12 MPa (122 kgf / cm ² ),
Nozzle tip # 729 (made of gray), spraying distance 30c
m, pump 45: 1 (manufactured by GRACO) was sprayed, and the pattern width, surface texture, and discharge amount were checked and judged. <Storage stability> The storage stability was evaluated by the increase in viscosity after treatment at 35 ° C for 240 hours. <Baking Dryability> After coating the sample on the electrodeposition plate and leaving it at room temperature for 10 minutes, preliminary drying is performed at 90 ° C. for 10 minutes, and further main baking is performed at 140 ° C. for 20 minutes to swell the coating surface. The generation of cracks was visually observed and the coating film thickness without swelling and cracking after drying was determined. <Viscosity> BH type viscometer using No. 7 rotor, 20 rp
m, measured at 20 ° C.

[0032]

[Table 1] Styrene-butadiene copolymer resin (1) Solid content 58%, viscosity 150 cps, average particle size of latex 0.3 μm. Styrene-butadiene copolymer resin (2) Solid content 43%, viscosity 150 cps, average particle size of latex 0.1 μm.

[Examples 2 and 3 and Comparative Examples 3 and 4] Emulsion type paints were prepared so that the viscosity was the same with the components and blending amounts shown in Table 2, and sprayability and storage were performed in the same manner as above. The stability and printability were evaluated. The results are also shown in Table 2.

[0034]

[Table 2] (3) Solid content 59%, viscosity 170cps, emulsion average particle size 0.35μ (4) Solid content 44%, viscosity 165cps, emulsion average particle size 0.08μ (5) Solid content 62%, viscosity 175cps, emulsion average particle Diameter 0.39μ (6) Solid content 45%, viscosity 170cps, emulsion average particle size 0.11μ

From the results shown in Tables 1 and 2, when a latex having a large polymer particle size and a high solid content was used, baking drying property was remarkably improved, and a thick film was formed without cracking or swelling during drying. It is recognized that it can be formed. It is also recognized that the dry coating film specific gravity can be reduced by blending glass balloons.

[0036]

The anti-chipping paint for automobiles of the present invention comprises:
It is possible to form a thick film without generating cracks or swelling during dry baking, and reduce the specific gravity of the coating film.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location C09D 133/04 PGD 201/00 PDC // C08K 7/22 KCL (72) Inventor Naokazu Yamamura Aichi 1 Toyota Town, Toyota City, Japan Toyota Motor Co., Ltd.

Claims (2)

[Claims] 1. An emulsion-type coating material comprising polymer particles as a coating film component, which is mainly composed of latex emulsified and dispersed in water as emulsion particles, wherein the emulsion particles have an average particle diameter of 0.3 μm or more, and A chipping-resistant coating material for automobiles, characterized in that the latex has a solid content of 50% by weight or more and contains hollow fine particles as a filler. 2. The anti-chipping paint for automobiles according to claim 1, wherein the polymer as the coating film component is an acrylic resin or a styrene-butadiene copolymer resin having a styrene content of 15 to 50%.