JPH07166098A - Aqueous-emulsion paint - Google Patents

Abstract

PURPOSE:To enable a weight reduction in an automobile by providing an aqueous-emulsion paint which gives a coating film having high strength and capable of having a reduced specific gravity and satisfactory chipping resistance, etc., even when containing glass balloons. CONSTITUTION:This paint comprises an aqueous emulsion of a polymer serving as a film-forming ingredient and further contains a super mol.wt. polymer having an average mol.wt. of 4X10<6> or higher.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous emulsion paint suitable as an undercoat paint for automobiles.

[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 generates hydrogen chloride when incinerated, it is environmentally problematic.

For this reason, paints replacing polyvinyl chloride plastisols have been demanded, and water-based emulsion paints using water as a dispersion medium have been attracting attention as paints in line with this.

Further, it has been conventionally desired to reduce the weight of automobiles, and paints are also required to form coating films having as low specific gravity as possible. In this case, it is known that the specific gravity can be reduced by replacing a part of the filler compounded in the paint with a glass balloon, but when the glass balloon is compounded in the aqueous emulsion paint, the specific gravity of the coating film is reduced. However, there is a problem that the strength is lowered and the chipping resistance is lowered.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an aqueous emulsion paint capable of forming a coating film having high strength and excellent chipping resistance.

[0006]

Means for Solving the Problems The present inventor has conducted extensive studies to solve the above-mentioned object, and as a result, compared with an aqueous emulsion coating composition obtained by dispersing a polymer as a coating film component in water, It has been found that the coating film can be made to have high strength by incorporating an ultrahigh molecular weight polymer having a molecular weight of 4 × 10 ⁶ or more.

That is, by blending a polymer having an ultrahigh molecular weight, the polymers are entangled with each other and the loss of the polymers is reduced, whereby a coating film having high strength and high elongation can be obtained, and repeated elongation is achieved. Without causing a decrease in elastic modulus due to shrinkage, in this case even if a part of the filler is a glass balloon, it has sufficient strength and can reduce the specific gravity of the entire dry coating film without affecting the chipping resistance and the like. The inventors of the present invention have found that they can do so and have completed the present invention.

Therefore, the present invention is characterized in that an aqueous emulsion paint prepared by dispersing a polymer as a coating film component in water is blended with an ultrahigh molecular weight polymer having an average molecular weight of 4 × 10 ⁶ or more. An aqueous emulsion paint is provided.

The present invention will be described in more detail below. The ultra-high molecular weight polymer of the present invention has an average molecular weight of 10 times or more that of a resin used in a usual aqueous emulsion, specifically 4
A material having a density of × 10 ⁶ or more is used, and particularly preferably a density of 5 × 10 ⁶ or more. As the ultra-high molecular weight polymer in this case, acrylic, SBR, BR resins and the like can be used, and the blending amount thereof is 5 to 8 of the resin solid content.
It is preferably 0% (% by weight, the same applies hereinafter), particularly 10 to 50%.

In the present invention, the above-mentioned ultra high molecular weight polymer may be used alone, or may be used in combination with one or more kinds selected from usual polyurethane resin, acrylic resin, styrene-butadiene rubber and the like. . Note that these polymers are preferably dispersed in water with a solid content as high as possible in order to reduce the amount of water to be evaporated, and specifically, it is desirable that the content of the polymer is 50% or more in the paint.

A glass balloon may be added to the aqueous emulsion paint of the present invention. In this case, the amount of glass balloons added is preferably 5 to 40%, particularly 10 to 20% of the total filler. Further, if the addition amount is less than 5%, the specific gravity cannot be sufficiently reduced, and if it is more than 40%, the strength is remarkably lowered and the chipping resistance may not be secured. The average particle size is preferably 40 to 70 μm in consideration of sprayability and the like.

Examples of the filler include calcium carbonate, talc, clay, silica, diatomaceous earth, zeolite, magnesium carbonate, mica, etc. However, if the filler has a flat particle shape, water vaporization is prevented. Of these, calcium carbonate and diatomaceous earth, which have non-planar particle shapes, are preferred because they tend to interfere. The average particle size of the filler is preferably 1 to 20 μm.

The blending amount of the filler containing glass balloons is 50 to 300 parts, especially 15 parts with respect to 100 parts of the resin solid content.
The range of 0 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.

In addition to the above components, the aqueous emulsion coating composition of the present invention may contain a defoaming agent, a thickener, a dispersant, a wetting agent, etc., if necessary.

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

The thickening agent is for helping the dispersion of the filler to prevent sedimentation, improving the stability of the coating material, finishing the preparation of an appropriate viscosity, and obtaining the balance of both sprayability and thixotropy. For example, methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, protein, polyvinyl alcohol, sodium acrylate, etc. 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 various kinds of sodium polyphosphates, surfactants and the like can be exemplified, and they can be used in a usual dose.

The aqueous emulsion paint of the present invention can be prepared by mixing the above components. For example, resin components (latex), fillers, dispersants, wetting agents, etc. are kneaded, then a thickener is added to disperse them, and then a defoaming agent is added to defoam and finally filtered. The aqueous emulsion coating composition of the present invention can be prepared. As the disperser, a high speed disperser is suitable, and since the kneading and the viscosity adjustment afterward can be performed at the same time, the production efficiency can be made higher than that of other machines.

The aqueous emulsion coating composition of the present invention can be used as an undercoat coating composition for automobile tire houses, under floors, front aprons and the like, and also as a sealing material for seams of seals.

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 coating material after drying.
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.

[0022]

EFFECT OF THE INVENTION The water-based emulsion coating composition of the present invention has a high strength, and even if glass balloons are added, it is possible to achieve a reduction in specific gravity without impairing chipping resistance and the like, thereby reducing the vehicle body weight. You can

[0023]

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.

[Examples 1 to 3 and Comparative Examples 1 to 3] The components shown in Table 1 were mixed in the compounding amounts shown in the table, and the specific gravity of the obtained sample after baking and drying and the chipping resistance were evaluated. The results are also shown in Table 1. <Chiping resistance> A sample was coated on a steel plate so that the film thickness after drying was 500 μm, left at room temperature for 10 minutes, pre-dried at 90 ° C. for 10 minutes, and then baked at 130 ° C. It went for 20 minutes.

The above-mentioned baked sample was set at an angle of 60 ° from the horizontal with the coated surface facing upward, and the lower end of a polyvinyl chloride pipe having an inner diameter of 20 mm and a length of 2 m was placed vertically on this coated surface, and this pipe was applied. The M-4 nut specified by JIS was dropped from the upper end of the pipe through the pipe, and the total weight of the nut until the base material was exposed was measured.

[0026]

[Table 1]

From the above results, it was confirmed that by using the ultra high molecular weight polymer, good chipping resistance can be provided even when used in combination with the glass balloon, and the specific gravity of the coating film can be reduced.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C09D 201/00 PDC // C08K 7/28 KCL

Claims (2)

[Claims] 1. A water-based emulsion paint comprising a polymer as a coating film component dispersed in water, having an average molecular weight of 4 ×.
An aqueous emulsion paint characterized by being blended with an ultra high molecular weight polymer of 10 ⁶ or more. 2. The paint according to claim 1, wherein a glass balloon is blended.