JP3408853B2 - Aqueous emulsion paint - Google Patents

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 paints for undercoats of automobiles. However, when the automobiles are scrapped and the steel sheets are regenerated, the coating films may be removed by incineration. Many. 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.

However, the aqueous emulsion paint has a problem that it is difficult to form a thick film. That is, when the water-based emulsion-based paint is applied thickly, when it is heat-dried (baked), water evaporation due to the drying occurs from the surface,
As a result, the skin of the coating film is fused with emulsion particles, which prevents the evaporation of water in the undried coating film, resulting in cracks and swelling of the coating film. There's a problem. Therefore, when baking an aqueous emulsion paint, the baking temperature of the vinyl chloride-based plastisol is 140 ° C. for about 30 minutes, while the heating rate of the baking furnace is set to prevent such cracking and swelling. Although the condition is adopted that the temperature is lowered and the furnace temperature is lowered to about 70 to 90 ° C., such a condition causes a decrease in productivity.

In order to solve such problems, an aqueous chipping-resistant coating composition containing an organic polymer heat-sensitive gelling agent and a filler has been proposed in JP-A-5-32938. Emulsion paint containing organic polymer heat-sensitive gelling agent is a polymer that starts gelation rapidly when the temperature exceeds the cloud point of heat-sensitive gelling agent by heating when coating is dried and baked. The particles are fused and the water between the particles is discharged to complete the film formation in a short time. The water discharged on the surface due to the film formation evaporates quickly, so that it dries very quickly.By blending such an organic polymer heat-sensitive gelling agent, even when a thick film is formed, swelling during high temperature baking and It has been shown that cracking can be prevented.

[0006]

However, as a result of a detailed study by the present inventor of an aqueous emulsion paint containing an organic polymer heat-sensitive gelling agent, it was found that there are various problems. That is, since the organic polymer heat-sensitive gelling agent is a polymer, it increases the viscosity of the aqueous solution,
In order to keep the viscosity of the compound within the sprayable range, it must be added as a dilute aqueous solution, resulting in a large amount of water in the aqueous emulsion paint, which adversely affects the drying property, and It did not show the sufficient effect.

Moreover, the organic polymer heat-sensitive gelling agent has poor storage stability, and in practice, it is necessary to use a surfactant as a stabilizer in order to stabilize the latex. However, in order to increase the viscosity, a dilute aqueous solution has to be used, and there is a problem that the above-mentioned drying property is adversely affected.

Therefore, the above proposal is still insufficient to prevent cracks and swelling when forming a thick film of an aqueous emulsion paint.

The present invention has been made in view of the above circumstances, and has good storage stability, can quickly prevent evaporation and evaporation of water during dry baking, and can effectively prevent cracks and swelling, thereby forming a thick film. It is an object of the present invention to provide a water-based emulsion paint that can be used.

[0010]

Means and Actions for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventor has found that in an aqueous emulsion coating composition in which a polymer as a coating film component is dispersed in water It is effective to blend a molecular heat-sensitive gelling agent and a polyamine, and such an aqueous emulsion paint has good storage stability, and moisture evaporates quickly during drying, causing abnormalities such as cracks and swelling. It was found that it is difficult and thick film can be easily formed.

That is, although the organic polymer heat-sensitive gelling agent can obtain the heat-sensitive gelling effect by adding a relatively small amount, it has the above-mentioned problems, while the polyamine (a kind of heat-sensitive gelling agent) is used. Is cheap and easy to dilute in water,
In addition, it has a low viscosity, and the amount of water brought in by addition is small, so the increase in water content is small, but it is unstable at room temperature when added in large amounts because it gives a heat-sensitive gelling effect by destabilizing the charge of the emulsion. become,
The storage stability was poor, the condition setting was difficult, and there was a problem in practical application.

However, when both are used together, the problem of increase in viscosity of the organic polymer heat-sensitive gelling agent and the problem of storage stability of the polyamine are solved, and by using both together, the problems that each had are solved and these heat-sensitive gels are solved. The present inventors have found that the original effect of the agent is exhibited and that the path to practical use is opened, and the present invention has been completed.

Therefore, the present invention is an aqueous emulsion coating composition in which a polymer as a coating film component is dispersed in water, wherein an organic polymer heat-sensitive gelling agent and a polyamine are blended. I will provide a.
Hereinafter, the present invention will be described in more detail. The aqueous emulsion-based coating material of the present invention is obtained by dispersing a polymer as a coating film component in water as described above.

The polymer is not particularly limited, and any polymer that can be used as a coating film component of an aqueous emulsion paint can be used, and examples thereof include polyurethane resin, acrylic resin, and styrene-butadiene rubber. These polymers are preferably dispersed in water with a high solid content as much as possible in order to reduce the amount of water to be evaporated, and specifically, it is preferably 50% (% by weight, the same applies hereinafter) or more in the latex.

The aqueous emulsion paint of the present invention is characterized in that the organic polymer heat-sensitive gelling agent and the inorganic heat-sensitive gelling agent / polyamine are used in combination as described above.

As the organic polymer heat-sensitive gelling agent, specifically, starch and its derivatives, alkylene oxide adducts of nonionic activator organopolysiloxanes, alkylphenol-formalin condensates of organopolysiloxanes, and alkylphenol-formalin condensates. Examples thereof include alkylene oxide adducts, polyvinyl methyl ether, and organopolysiloxane polyether copolymers. These can be used alone or in combination of two or more.

The addition amount of the organic polymer heat-sensitive gelling agent is not particularly limited, but it is 0.
It can be appropriately selected from the range of 2 to 3 parts, particularly 0.4 to 2 parts. If the amount added is less than 0.2 parts, the effect added may not occur, while if added more than 3 parts, the storage stability at room temperature will be poor, resulting in a marked increase in viscosity, or bringing in dilute solution of water. The amount of water increases and the amount of water in the compound increases, which may hinder the thickening of the film during baking.

On the other hand, as the inorganic heat-sensitive gelling agent, specifically, sodium hexametaphosphate, ammonium nitrate, ammonium chloride, sodium carbonate, potassium carbonate, sodium sulfate, potassium chloride, calcium chloride, calcium sulfate, zinc ammonium complex salt, sodium nitrate, Lead nitrate,
Sodium acetate, etc. may be mentioned, and one of these may be used alone or 2
One or more species can be used in combination. Among these, sodium hexametaphosphate has a mild ability to destabilize the charge of the emulsion as compared with other inorganic heat-sensitive gelling agents, so it is easy to handle, and if it remains in the film after drying and curing, Since the deterioration of water resistance is less than that of metal salts, it can be mentioned as a preferable example.

The amount of the inorganic heat-sensitive gelling agent added is preferably in the range of 0.2 to 4 parts, particularly 0.5 to 2 parts, relative to 100 parts of the polymer solid content. If the blending amount is less than 0.2 parts, the effect of blending the heat-sensitive gelling agent may not be obtained. On the other hand, if it is more than 4 parts, the charge of the emulsion is destabilized and the storage stability at room temperature deteriorates. , It may cause a significant increase in viscosity.

The polyamine is a compound having two or more amino groups in one molecule and may be any as long as it is water-soluble. Due to the amino group in the molecule, such a polyamine has a function as a heat-sensitive gelling agent as well as a function as a cross-linking agent, and has the effect of improving the water resistance of the coating film after baking. Specific examples of such polyamines include diethylenetriamine, ethylenediamine, tetramethylenediamine, hexamethylenediamine, and triethylenetetramine, and one of these may be used alone or in combination of two or more. It is possible to use it together with the above-mentioned inorganic heat-sensitive gelling agent.

The amount of polyamine added is such that the polymer solid content is 1
It is preferably in the range of 0.2 to 4 parts, especially 0.2 to 1 part with respect to 00 parts. If the blending amount is less than 0.2 parts, the blending effect may not occur, while if it is more than 4 parts, the polyamine generally partially decomposes at a temperature of about 120 ° C. or higher to cause the generation of amine. Bubbles may form in the film.

In addition to the above-mentioned components, a filler, a defoaming agent, a thickener, a dispersant, a wetting agent and the like can be added to the water-based emulsion paint of the present invention, 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 filler content is 1 polymer solids.
50 to 300 parts, especially 150 to 250 parts for 00 parts
A range of parts is preferred. 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 performance may be deteriorated to make the coating film performance unsatisfactory, 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 formed, because low viscosity emulsions and emulsion mixtures tend to produce bubbles by stirring.

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 a 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 examples thereof include various sodium polyphosphates and surfactants, which 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, after latex, filler, dispersant, wetting agent, etc. are kneaded, a heat-sensitive gelling agent, a thickening agent, etc. are added to disperse, and then a defoaming agent, etc. is added to defoam and finally filtered. Then, the aqueous emulsion-based coating material of the present invention can be prepared. In this case, since the heat-sensitive gelling agent easily reacts when the temperature during mixing rises, it is desirable to add the heat-sensitive gelling agent as late as possible and to cool the temperature of the mixture before addition to 40 ° C. or lower. 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 water-based 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 sealing seams.

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.

[0032]

EFFECTS OF THE INVENTION The water-based emulsion coating composition of the present invention has good storage stability and quickly vaporizes water during drying and baking, so that a thick film can be formed without cracking or swelling. .

[0033]

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 Examples 1 to 14] Aqueous emulsion coatings were prepared with the formulations shown in Tables 1 and 2, and the viscosity, baking and drying resistance, water resistance and storage stability were evaluated according to the following methods. The results are shown in Tables 1 and 2 together with the solid content of the prepared water-based emulsion paint. The formulations in Tables 1 and 2 are shown in parts by weight in terms of solid content. <Viscosity> BH type viscometer using No. 7 rotor, 20 rpm, 20
It was measured at ° C. <Baking and Drying Properties> The sample was applied on a steel plate that had been electrodeposition coated, left at room temperature for 10 minutes, then pre-dried at 90 ° C for 10 minutes, and then main baking was performed at 140 ° C for 20 minutes. The swelling and cracking of the film surface were visually observed, and the coating film thickness without swelling and cracking after drying was determined. <Water resistance> A sample was coated on a steel plate that had been electrodeposited so that the film thickness after drying was 500 μm, and allowed to stand at room temperature for 10 minutes, then pre-dried at 90 ° C. for 10 minutes, and then the The baking was performed at 130 ° C. for 20 minutes. The above-mentioned baked sample was set at an angle of 45 ° from the horizontal with the coated surface facing upward, and the lower end of a vinyl chloride pipe having an inner diameter of 20 mm and a length of 2 m was placed vertically on this coated film surface, and the pipe was applied from the upper end of this pipe. The M-4 nut specified in JIS was dropped through the inside, and the total weight of the nut until the base material was exposed was measured to determine the initial chipping resistance. Next, after the baking sample was treated with warm water of 40 ° C. for 10 days, the above test was conducted on the sample left at room temperature for 2 hours, and the chipping resistance after water resistance was determined. It was evaluated according to the standard. ⊚: Very good ◯: Good Δ: Inferior ×: Remarkably inferior <Storage stability> The prepared paint was evaluated according to the following criteria by the increase in viscosity after the treatment for 240 hours at 35 ° C. ◎: good ○: slightly thickened △: thickened ×: gelled

[0035]

[Table 1]

[0036]

[Table 2]

From the results of Tables 1 and 2, when the heat-sensitive gelling agent was not added at all (Comparative Example 1), the baking and drying properties were extremely poor, and when only the polymer heat-sensitive gelling agent was added (Comparative Example 2).
Nos. 9 to 9) have almost no compounding effect when the compounding amount is small (Comparative Examples 2, 5, and 7), and the solid content decreases when the compounding amount is increased, and baking drying property is not sufficient (comparative). Examples 4, 6, 8). Moreover, when only the inorganic heat-sensitive gelling agent was blended (Comparative Examples 10 to 13), if the blending amount was small, there was almost no blending effect (Comparative Examples 10 and 12), and if the blending amount was large, the solid content was large but storage The stability is poor and the baking drying property is not sufficient (Comparative Examples 11 and 13).
Furthermore, when a large amount of polyamine was blended alone (Comparative Example 1)
In 4), it is recognized that decomposition occurred and bubbling occurred during baking.

On the other hand, an aqueous emulsion coating composition in which a polymer heat-sensitive gelling agent and a polyamine are used in combination (Example)
Is high in solid content, has extremely good baking and drying properties, has good storage stability, and it is recognized that at least the effects of the polymer heat-sensitive gelling agent and the polyamine are sufficiently exerted. To be

Front page continued (72) Inventor Haruji Shibata 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Corporation (72) Inventor Naokazu Yamamura 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Corporation (56) References JP-A-5-331387 (JP, A) JP-A-5-311095 (JP, A) JP-A-5-32938 (JP, A) JP-A-54-8638 (JP, A) JP-A-55 -144044 (JP, A) JP 59-25753 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C09D 201/00 C09D 5/00 C09D 5/02 C09D 7/12

Claims (2)

(57) [Claims] 1. An aqueous emulsion-based coating composition comprising a polymer as a coating film component dispersed in water, wherein an organic polymer heat-sensitive gelling agent and a polyamine are blended. 2. The water-based emulsion paint according to claim 1, wherein 0.2 to 3 parts by weight of the organic polymer heat-sensitive gelling agent and 0.2 to 4 parts by weight of the polyamine are blended with 100 parts by weight of the polymer solid component. .