KR19980059113A - Baking Curable Water-Based Coating Composition - Google Patents

Abstract

The present invention relates to a small-curing water-based coating composition, and more particularly, a reactive acrylic emulsion resin into which a reactor is introduced and a crosslinking resin are mixed to form a heat-curable three-dimensional network structure and impart water repellency to the surface of the coating film, thereby providing durability and water resistance. The present invention relates to a small hardening water-based coating composition which is very useful for anti-corrosive coating parts and high gloss home appliances by improving corrosion resistance, coating appearance, glossiness, and the like.

Description

Baking Curable Water-Based Coating Composition

The present invention relates to a small-curing water-based coating composition, and more particularly, a reactive acrylic emulsion resin into which a reactor is introduced and a crosslinking resin are mixed to form a heat-curable three-dimensional network structure and impart water repellency to the surface of the coating film, thereby providing durability and water resistance. The present invention relates to a small hardening water-based coating composition which is very useful for anti-corrosive coating parts and high gloss home appliances by improving corrosion resistance, coating appearance, glossiness, and the like.

In the industrial paint, heat-curable oil-based paint is mainly used to improve the productivity of the coating line, high durability of the coated product, and maintain a beautiful coating appearance.

However, the problems of global environmental protection and air pollution prevention, which began in the late 1980s, have become important issues in society, and the paint industry is also required to develop pollution-free, non-toxic, high quality and high performance paints.

With the strengthening of environmental regulations including the emission control of VOC (Volatile Organic Compounds), which is spreading in developed countries, the use of low solid solvents, which currently occupies most of the domestic industrial paint market, will decrease rapidly. It is expected.

In order to prepare for VOC regulations, which began in developed countries in Europe and North America, automakers in developed countries are accepting primer surfacers that do not significantly affect the appearance and aqueous phase of metallic base paints with high solvent emissions. Paint stability, foaming due to evaporation of water, sagging, paintability, deterioration of physical properties due to containing a large amount of hydrophilic groups, etc. have been shown as problems.

One of the representative water-based paints is electrodeposition paint, which is rapidly spreading as a primer for metal materials related to automobiles and home appliances because it has advantages of productivity, resource saving, quality uniformity and high performance, paint efficiency and low pollution. There are disadvantages that are used only in limited fields due to problems such as the price of paint, the cost of painting equipment and operating costs, the inability to use as top coat due to gloss, and the simplicity of color.

General industrial fields can be categorized into industrial machinery, large vehicles, building materials, electrical equipment, and metal secondary products. Painting in this area can be improved in appearance, antirust performance, appropriate drying conditions, and various colors. In addition to the application, there is a strong demand for rationalization of the painting work, improvement of the painting environment, and preparation for the risk of fire.

However, although the use of water-based paints as anti-pollution paints has been expanded, products using condensation reaction curing mechanisms of water-soluble alkyd or water-soluble acrylic resins and amino (melamine, urea, benzoguamine resins, etc.) resins are generally used. It is known that such water-based coating composition is water-resistant, salt-water spray resistance, water-resistant of the dry coating film by using a resin in which a large amount of hydrophilic groups (-OH, -COOH, -NH _2, etc.) is introduced into the resin polymer skeleton for water solubilization The chemical properties and the like are extremely poor compared to oil-soluble paints, and in particular, there is a problem in that the glossiness of the coating film and the beauty of appearance are insufficient.

In addition, in the case of the paint composition described above, a separate dispersant is used for dispersion and stabilization of the pigment, or a surfactant and a pigment dispersant containing a water-soluble component are used, and these components remain in the dry coating film to oxidize the metal material. Not only has the problem of lowering the anti-corrosion function, lowering the water resistance and corrosion resistance of the dry coating film, but also the coating workability (e.g. foaming, flow , Condensation, etc.) are poor, and the appearance of the coating film such as dichroism, staining, gloss reduction, and the like is poor.

In the case of such a conventional hardening type water-based coating composition, there is room for improvement in corrosion resistance and hot water resistance, and there is a critical problem in that the degree of gloss and the appearance level of the dry coating are significantly different from those of the conventional solvent type coating. .

Therefore, the present invention is a styrene-modified acrylic having a reactor (-OH, -COOH) in the polymer skeleton in order to solve the problems of water resistance, corrosion resistance and problems of the conventional small-curing water-based coating composition as described above and to improve the gloss of the dry coating, and improve the appearance By heat curing using an emulsion resin and high solid hexamethoxymethylmelamine resin having excellent crosslinking properties, a three-dimensional network structure is formed, hydrophilic groups are removed from the polymer skeleton, and a separate dispersion emulsion resin is The purpose of the present invention is to provide a water-curable water-based coating composition with a new composition which improves durability, water resistance, corrosion resistance, coating appearance improvement, gloss, etc., which are problems of existing waterborne coatings by providing water repellency to the coating film surface.

The present invention is a styrene-modified acrylic emulsion resin having a reactor (-OH) at the end of the resin, hexamethoxymethylmelamine (HMMM) -based crosslinking resins, coloring pigments, pigment dispersion auxiliary resin, dispersant, antifoaming agent, pH control agent, leveling agent , Aqueous curing type aqueous coating composition comprising a coating forming solvent, a thickening agent, an anti-rusting agent, a water repellent, and ion-exchanged water, wherein the acrylic emulsion resin containing a hydroxyl group (-OH) as a provider and pigment dispersion Auxiliary resin 35 ~ 70 wt%, crosslinking resin 2.5 ~ 15.5 wt%, coloring pigment 1.5 ~ 22.0 wt%, antirust agent 0.5 ~ 6.0 wt% of two or more components, leveling agent 0.01 ~ 2.0 wt%, coating film forming aid 5 to 10 wt% of a solvent, 0.5 to 3.0 wt% of a thickener, 0.3 to 2.0 wt% of an antifoaming agent, 0.1 to 1.0 wt% of a water repellent, and 20 to 40 wt% of ion-exchanged water.

Hereinafter, the present invention will be described in more detail.

The acrylic emulsion resin solids used as a binder is a styrene-modified acrylic emulsion resin in which the composition ratio of styrene monomer, alkyl acrylate, and hydroxyalkyl methacrylate is 35 to 45:45 to 50: 5 to 10 wt%. Solid content is 48-52% by weight, ion-exchanged water is 48-52% by weight, pH (pH) is 8.0-10.0, acid value is 35-55, fish value is 30-50, and glass transition temperature (Tg) is 30 ℃ or less Should be.

If the acid value is too low, the stability against water solubility is lowered. If the acid value is too high, the hydrophilicity of the dry coating film is large, and thus, the hot water resistance and the saline water spray resistance are deteriorated.

If the hydroxyl value is too low, the reactivity with the crosslinking resin is lowered, and the strength and physical properties of the coating film are sufficiently lowered. If the hydroxyl value is too high, the low temperature hardenability is excellent, but the impact resistance of the coating film is lowered, and the resistance against salt spraying is extremely low. It becomes bad.

The pigment dispersion auxiliary resin is an acrylic emulsion resin, which is composed of styrene monomer, alkyl acrylate and alkyl methacrylate at 45 to 60:15 to 25:25 to 35% by weight, and the average particle size of the emulsion is 80 nm or less. And glass transition temperature (Tg) of 25 ~ 35 ℃ should be used.

If the deviating from this limitation, the dispersion effect and dispersion stability of the pigments added together are not only deteriorated, but also it is not possible to prevent the breakdown of the emulsion due to the impact of the physical force transmitted when passing through the dispersion apparatus.

As the HMMM resin used as the crosslinking resin, for example, Cymel 300, 303, 327, 385, etc. of American Cinnamid may be used.

As a dispersant used to enhance the wettability of the pigment, preventing reaggregation, sedimentation, and dispersing effect, block copolymers having a pigment affinity (for example, Disper BYK-181, 182, 184, 190, etc.) may be used. And there is a problem that the stability retention effect is poor, pigment reaggregation and sedimentation occur, and the hot water resistance and corrosion resistance is lowered.

Colored pigments can be selected from all organic and inorganic pigments that can be solubilized and used within the range of 1.5 ~ 22.0% by weight depending on the type of pigment in consideration of hiding power of dry coating.

In addition, as the antifoaming agent, a modified polysiloxane mixture is used, which has an effect of preventing foaming during the manufacturing of paints and an effect of antifoaming during painting, and the use of a small amount reduces the occurrence of foaming and the defoaming effect, and the use of an excessive amount of coating defects (cratering). There is a high possibility of occurrence, and the adhesion between layers of repainting of the dry coating film is lowered.

As a neutralizing agent for maintaining paint stability, for example, ammonia (NH ₄ OH), TEA (triethylamine), DMAE (dimethylaminoethanol), etc. are used. It is used to adjust the pH to prevent the initial rust of the material, the range is about 7.5 ~ 9.5 is a general stabilization range.

Meanwhile, in the present invention, two or more components may be used as a flash rust inhibitor, for example, sodium nitrate, ammonium benzoate, ammonium dichromate, and the like, and components such as zinc, zirconium, calcium, and barium may be used. Corrosion Inhibitors of organic complexes can be mixed at the same time to increase anti-corrosion effect, and to prevent the expansion of corrosion and the formation of Blister on the surface of coating film in salt spray test. The effect is increased.

In addition, the leveling agent used to prevent the wettability of the material and the spreading (leveling effect) of the coating film and the cruttering (polyether-modified dimethylpolysiloxane) may be used, and the film forming aid for the film forming assistance function and freezing prevention effect. Zero butyl cellosolve, butyl carbitol, ethylene glycol, propylene glycol, etc. may be used. When these components are excessive, the coating film dryness and coating hardness are reduced. Falls.

As thickener, water dispersible acrylic-acrylic acid copolymer may be used, which requires the control of PH (between 7 and 10) at the time of inputting, and the viscosity of the paint is used to control the viscosity and fluidity of the paint. By controlling, it prevents the coating (Sagging) of the coating film, assists in the rise of saliva, prevents the settling of pigment in the paint and maintains a stable dispersion state of the pigment.

The water repellent may be a powdered or emulsion-type aqueous wax. For example, Aquabead 519, 916, 270E and the like (manufactured by US MICRO POWDERS, INC.) May be used as trade names.

As such, the bake-curable water-based coating composition using the reactive emulsion resin prepared according to the present invention generally has the following general characteristics and coating specifications, so that it may be used by coating the coating with an appropriate method.

[General nature]

(1) Finish: Glossy (Gloss 60 ° / 85% or more)

(2) Color: Any color

(3) Drying condition: It is a general specification condition as following table 1.

Baking temperature 120 ℃ 150 ℃ Remarks Baking time 30 minutes 15 minutes Heat drying is based on hot air circulation. 2. Temperature conditions are based on material surface temperature (MPT). 3. Coating thickness is based on DFT 30 ~ 40 microns with one coat.

(4) Specific gravity: 1.00 to 1.40 (difference by color)

(5) Non-volatile matter: 40-65% (difference by color)

(6) pH (pH): 8.0-9.5

[Painting specifications]

(1) surface coating

· Thoroughly remove and paint the rust, dust, oil and other contaminants of the coating.

Appropriate chemical coating (zinc phosphate, iron phosphate, chromate chemical coating) can further increase adhesion and corrosion resistance.

(2) Prepainted: None (A suitable oily or water based antirust coating may be applied if necessary.)

(3) coating conditions

Appropriate temperature is 15 ~ 25 ℃ and relative humidity is 40 ~ 70%.

(4) dilution

Immersion coating time: 20-40 seconds (Ford Cup # 4, 25 ℃)

Air spray coating: 25 ~ 45 seconds (Ford Cup # 4, 25 ℃)

· After mixing pure water or ion-exchanged water with raw material properly and stirring, apply paint

· The working viscosity may vary depending on the painting method and working conditions, the shape of the workpiece, and the working conditions. Use diluent (pure or ion exchanged water) as appropriate.

(5) Coating method: immersion coating, spray painting, airless spray painting

(6) Recommended dry film thickness: 30-40 microns by one painting

(7) Subsequent painting: None.

(8) Storage period: about 6 months (sealed in a cool, dark place)

Hereinafter, the present invention will be described in detail with reference to the following Examples, which are not intended to limit the scope of the present invention.

[Examples 1 and 2]

The paint composition was composed of the composition of the following Table 2.

In order to prepare the composition, the ingredients of Nos. 1 to 6 are sequentially added to the mixing tank, mixed, and dispersed at a prescribed particle size (10 microns) or less with a disperser (sand mill). At this time, the temperature of the dispersion is controlled using a cooling device so that the temperature of the dispersion during the dispersion process is 40 ℃ or less.

Thus, while slowly dispersing the dispersion solution is dispersed at 200rpm at a low speed slowly and gradually added a small amount of components of the numbers 7-17 while strictly observing the order to ensure uniform mixing through complete stirring at least 500rpm.

After the stirring was completed, the stirring tank was sealed, left to stand for at least 12 hours, aged, and then packaged.

Comparative Examples 1-2

Comparative Example was carried out in the component composition of the following Table 3.

In order to manufacture the comparative example 1, the components of numbers 1-7 are mixed, and it disperse | distributes to a grain size below with a sand mill.

The components of Nos. 8 to 12 are sequentially added while stirring the dispersed dispersion at low speed, and when the addition is completed, the components are stirred at high speed to obtain a uniform mixed state.

In order to manufacture the comparative example 2, the components of numbers 1-7 are mixed, and it disperse | distributes to a grain size below with a sand mill.

In the same manner as in Comparative Example 1, the ingredients of Nos. 8 to 14 were added to complete the preparation.

In addition, the detailed manufacturing method of Comparative Examples 1-2 is performed similarly to the working method of an Example.

Experimental Example

For the paint composition prepared according to the above Examples and Comparative Examples, the physical properties were tested according to the following methods for the following test items, and the results are shown in Table 4 below.

However, in the test, the physical property test conditions were coated with zinc phosphate coated 0.8T CR steel, and the dry film thickness was coated based on 30 ~ 40 micron, dried at 130 ℃ for 20 minutes, and left at room temperature for 1 day, followed by item test. Proceeded.

As a result, the coating composition according to the present invention is excellent in appearance and gloss, excellent adhesion to the material, and excellent in rust resistance, durability, and chemical resistance, as well as various coating parts requiring high rust resistance, as well as high gloss. Not only can be applied to the required home appliances, it is possible to obtain excellent coating performance by drying at a low temperature (130 ° C.) than 150 ° C., which is a drying condition of conventional water-based paints.

Claims (7)

An aqueous coating composition containing acrylic resin as a main component, containing 35 to 70% by weight of an acrylic emulsion resin containing a hydroxyl group (-OH) and an auxiliary resin for dispersing pigments, and 2.5 to 15.5% by weight of a crosslinking resin, and coloring Pigment 1.5 ~ 22.0 wt%, 0.5 ~ 6.0 wt% of antirust agent of two or more components, 0.01 ~ 2.0 wt% of leveling agent, 5 ~ 10 wt% of coating film forming auxiliary solvent, 0.5 ~ 3.0 wt% of thickener, 0.3 ~ 2.0 wt of antifoam %, Water-repellent 0.1-1.0% by weight and 20-40% by weight of ion-exchanged water, the hardening type water-based coating composition. The method of claim 1, wherein the acrylic emulsion resin has a solid content of 35 to 45: 45 to 50: 5 to 10% by weight of styrene monomer, alkyl acrylate (Alkylacrylate) and hydroxyalkyl methacrylate (Hydroxyalkylmethacrylate) A styrene-modified acrylic emulsion resin comprised, wherein the acid value is 35 to 55, the hydroxyl value is 30 to 50, and the glass transition temperature (Tg) is 30 ° C. or less. According to claim 1, wherein the pigment dispersion auxiliary resin is an acrylic emulsion resin, the composition of the styrene monomer, alkyl acrylate and alkyl methacrylate is composed of 45 ~ 60:15 ~ 25:25 ~ 35% by weight, An average particle size of the emulsion is 80nm or less, glass transition temperature (Tg) is 25 ~ 35 ℃ characterized in that the hardening type water-based coating composition. According to claim 1, wherein the anti-corrosive agent is sodium nitrate or sodium benzoate and at least two corrosion inhibitors of organic salt compounds containing a metal component selected from zinc, zirconium, calcium and barium are mixed at the same time, the mixing ratio is 1: A small hardening water-based coating composition, characterized by a weight ratio of 1 to 10. The baking composition of claim 1, wherein the thickener is a water dispersible acrylic ester-acrylic acid copolymer. The method of claim 1, wherein the coating film forming auxiliary solvent is selected from butyl cellosolve, butyl carbitol, ethylene glycol, and propylene glycol. The method according to claim 1, wherein the water-repellent agent is a water-curing water-based coating composition, characterized in that the powder or emulsion-type aqueous wax.