JPS6016992B2 - water-based dispersion paint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an aqueous dispersion paint made by dispersing resin powder in water to form a slurry.

Powder coatings used in electrostatic coating methods for the purpose of low pollution are excellent in terms of film properties and economic efficiency, but on the other hand, they are difficult to melt during heating and melting after painting. Due to insufficient fluidity, there are defects in the smoothness of the coated surface, such as the orange skin, pinholes, eyeholes, and craters that are typical of powder coatings.

Further, in order to obtain a thin coating film, it is necessary to reduce the particle size of the powder, but in this case, the powder tends to become particles, so in the end, a thick film coating has to be applied. Furthermore, in addition to the large investment in painting equipment, there are safety and health problems such as the risk of dust explosion and dust inhalation, and economic problems such as the difficulty of collecting and reusing surplus sprayed powder. On the other hand, water-based dispersion paints, which are made by dispersing resin powder in water, are low-pollution like general powder paints, have good physical properties, and can be applied thinly. , spraying, which is a conventional method for painting equipment.

Since coating methods such as roll and dip can be used, there is no need for new equipment investment unlike with powder coatings for electrostatic coating.
The paint can be easily recovered, there is no risk of dust explosion, and it can be heated and melted to form a uniform coated surface. However, on the other hand, the above water-based dispersion paints have poor dispersion stability of the powder in water, making it impossible to maintain a constant quality for a long period of time, and there are also difficulties in painting workability. be. Therefore, an object of the present invention is to improve the dispersion stability of an aqueous dispersion paint made by dispersing resin powder in water.

That is, according to the present invention, there is provided an aqueous dispersion paint in which fine powder containing, as a film-forming main component, an epoxy group-containing resin mixed with a small amount of a carboxyl group-containing low-molecular compound is dispersed in water containing a volatile base. provided.

In the aqueous dispersion paint of the present invention, carboxyl groups are present on the surface of the fine powder, and the ionizability of these carboxyl groups in water is enhanced by the action of the coexisting base, resulting in a repulsive force between the carboxyl groups. This increases the dispersion stability of the powder, and at the same time lowers the viscosity of the paint and improves coating workability.

The carpoxyl group-containing low-molecular compound used in the present invention does not have an adverse effect on the melt flowability of the epoxy group-containing resin, which is the main component of the film formation, during competitive painting, and reacts with the main component resin to form a coating film. As a component, the resulting coating film has excellent smoothness and can maintain the desirable physical properties inherent to the main component resin.

The carboxyl group-containing low-molecular compounds used in the present invention include mono- or polycarboxylic acids with a molecular weight of 500 or less, a melting point of 30 to 25,000, and good melt fluidity, such as 1,
Preferred are 10-decanedicarboxylic acid, azelaic acid, sebacic acid, phthalic acid, stearic acid, lauric acid, capric acid, and the like. If the molecular weight is 500 or more, the molecular movement during melting becomes inactive, so the reactivity with the main component resin is low, and short-term baking is difficult. If the melting point is less than 3,000, the stickiness of the powder will increase and the powders will tend to bond together, while if the melting point is more than 25,000, it will be difficult to melt at normal baking temperatures and it will not be uniform with the main component resin. reaction becomes difficult. The proportion of the carboxyl group-containing low-molecular compound used is 2 to 20% of the epoxy group-containing resin, which is the main component for film formation.
The content is preferably 15% by weight. The epoxy group-containing resin used in the present invention is not particularly limited as long as it is a resin used as a general powder coating and contains an active epoxy group, but acrylic resins containing a glycidyl group and bisphenol type epoxy resins may be used. Resins can be used as preferred among them.

The volatile base used in the present invention is desirably one that is sufficiently volatilized and removed at the normal temperature of about 150 to 25,000 and does not remain in the resulting coating, such as ammonia,
Methylamine, ethylamine, dimethylamine, diethylamine, triethylamine, ethanolamine, ethylenediamine and the like are preferred.

To prepare the aqueous dispersion paint of the present invention, first, an epoxy group-containing resin, a carboxyl group-containing low-molecular compound, a coloring agent, and, if necessary, various conventional additives such as a fluidity regulator are uniformly mixed together. The powder is prepared by mechanical or chemical grinding methods known in the art and then dispersed in an aqueous solution containing a volatile base and optionally a small amount of a conventional surfactant. Just let it happen.

At this time, the amount of volatile base added may be adjusted such that the pH of the aqueous dispersion paint finally prepared is 6.5 to 7.0. The aqueous dispersion paint of the present invention produced in this way has excellent dispersion stability and coating workability, and can form a smooth coating film that maintains the desired physical properties of the main component resin. Next, the present invention will be specifically explained with reference to Examples.

It should be noted that all "%" in the examples means "% by weight". Example 1 To 2,000 ml of water, 30 ml of calcium phosphate, which had been prepared by adding equimolar amounts of calcium chloride to trisodium phosphate, was added, and the mixture was heated at a temperature of 8,000 ml for 70 ml. p. m.
Suspension and dispersion at a speed of ``Rapizol B-80''
(Surfactant manufactured by Nippon Oil & Fats Co., Ltd.) 0.81 g was added and uniformly dissolved.

On the other hand, "FINDIC 50-186" (acrylic resin containing chrycidyl group manufactured by Dainippon Ink Chemical Industries, Ltd.) 218
．． 52, "Epicote 1001" (epoxy resin manufactured by Shell Chemical Co., Ltd.) 10 days, 1,10-decanedicarboxylic acid 4
Toluene 45 in which "Corofin Black 909" (black pigment manufactured by Dainippon Ink & Chemicals Co., Ltd.) 8.42 and "Modaflow" (flow control agent manufactured by Monsanto Chemical Co., Ltd.) 2.8 ml were dissolved and dispersed on 0.7 pm. % solution was prepared. Next, 600 g of this 45% toluene solution was heated to 80 ml and dropped into the aqueous solution to disperse the cicadas for 15 minutes. After that, toluene is azeotropically distilled with water at 85 to 9,900 ℃ under normal pressure to completely distill it off, and then treated in a furnace. Afterwards, calcium phosphate adhering to the powder is dissolved and removed with dilute hydrochloric acid, and then wet distillation is performed. Almost quantitative amount of fine black acrylic resin powder was obtained. Next, this product was labeled as “Rapizol B-80”.
In the presence of 0.15% (based on solid content), add to water to a concentration of 55%, mix vigorously to form a slurry, and then add a small amount of ammonia to adjust the pH to 6.7. When adjusted, the viscosity of the slurry decreased significantly, and an aqueous dispersion paint showing stable dispersibility was obtained.

Although this paint separates into two layers even after being left at room temperature for two weeks, the powder in the lower layer remains in a soft precipitated state and can be easily and uniformly redispersed with a small amount of shedding. Comparative Example A black acrylic resin powder was obtained in the same manner as in Example 1 except that 1,10-decanedicarboxylic acid was omitted.

This powder was made into a paint by strongly mixing it with water to a concentration of 55% in the presence of 0.15% (based on solid content) of "Rapizol B-80", but this paint did not stand at room temperature. When left for a day and night, the powder separated into two layers, and the powder in the lower layer showed a hard precipitated state, and it was difficult to uniformly redisperse the powder if it was slightly concentrated. Example 2 Finedic 50-399M (glycidyl group-containing acrylic resin manufactured by Dainippon Ink Chemical Industries, Ltd.) 240 evenings, 1,
10-dicanedicarboxylic acid (20%), stearic acid (20%), "Corofin Black 909" (8.79%) and "Modaflow" (2.9%) were melt-kneaded in a kneader, cooled, and crushed in a crusher to obtain a particle size of approximately 40%. Obtained Buddha Powder.

Next, this product was mixed with "Rapisol B-80" 0.15
% (based on solid content), add it to water to a concentration of 50% and stir vigorously to form a slurry, then add a small amount of ammonia to adjust the pH to 6.8. An aqueous dispersion paint with a significantly reduced slurry viscosity and stable dispersibility was obtained.

Example 3 In Example 2, 1,10-decanedicarboxylic acid 20
When an aqueous dispersion paint was prepared in exactly the same manner except that 1 part of azelaic acid and 16 parts of stearic acid were used instead of 20 parts of azelaic acid and 20 parts of stearic acid, the slurry viscosity decreased significantly and stable dispersibility was exhibited. A water-based dispersion paint was obtained.

Example 4 In Example 2, 1,10-decanedicarboxylic acid 20
An aqueous dispersion paint was prepared in exactly the same manner except that 35% of stearic acid was used, and an aqueous dispersion paint with significantly reduced slurry viscosity and stable dispersibility was obtained.

Example 5 In Example 2, 1,10-decanedicarboxylic acid 20
Capric acid 36 instead of 20 and stearic acid
An aqueous dispersion paint was prepared in exactly the same manner except that the slurry was used, and an aqueous dispersion paint with significantly reduced slurry viscosity and stable dispersibility was obtained.

Claims (1)

[Claims] 1. A film with improved dispersibility characterized by being formed by dispersing fine powder containing an epoxy group-containing resin mixed with a carboxyl group-containing low-molecular compound as a main film-forming component in water containing a volatile base. Water-based dispersion paint.