KR20210013944A - Aqueous Coating Composition - Google Patents

Abstract

The present invention relates to an environmentally friendly water-soluble epoxy coating composition having excellent adhesion, drying properties and rust prevention properties.

Description

Water-soluble coating composition {Aqueous Coating Composition}

The present invention relates to an eco-friendly water-soluble coating composition having excellent adhesion, drying and rust prevention properties.

Industrial oil-soluble paints are applied to ferrous or non-ferrous metals and are used to secure the durability of materials, to realize excellent appearance and gloss, and to secure chemical resistance. As oil-soluble paints, a two-component epoxy primer composition and a two-component acrylic urethane top coat composition are generally used. For example, Korean Patent Application Publication No. 2019-0013592 discloses a coating composition containing an epoxy compound, an amine-based curing agent having a cyclic structure, an imidazole-based compound, and a pigment.

The oil-soluble paint has a problem of discharging a large amount of volatile organic compounds (VOC) during the manufacturing process and the painting process. Volatile organic compounds have a high vapor pressure and are easily evaporated into the atmosphere, causing a greenhouse effect, which can cause global warming, and may react with nitrogen compounds in the atmosphere to cause photochemical smog. Accordingly, regulations on the content of volatile organic compounds are gradually becoming stricter around the world, and accordingly, there is an increasing demand for an eco-friendly water-soluble paint with a reduced content of volatile organic compounds.

Meanwhile, in order to impart excellent durability to the coating film, mechanical properties such as adhesion, weather resistance, and impact resistance of the coating composition must be excellent. Accordingly, there is a need to develop a coating composition capable of reducing the content of volatile organic compounds and securing physical properties equal to or higher than those of conventional oil-soluble paints.

The present invention provides an eco-friendly water-soluble epoxy coating composition at the same time excellent in adhesion, drying and rust prevention.

The present invention provides a water-soluble epoxy coating composition comprising an epoxy resin, an amine or amide curing agent, and a silane compound.

The water-soluble epoxy coating composition according to the present invention provides excellent mechanical properties such as adhesion, dryness, and rust prevention, and provides an eco-friendly coating due to a low content of volatile organic compounds. The water-soluble epoxy coating composition of the present invention can be applied to various fields such as heavy equipment, transformers, and automobile parts, and can be applied to one coating or two coating systems. The water-soluble epoxy coating composition according to the present invention can be used as a base coating composition in a two-coating coating system, and can be used as a single coating when it is not exposed to the outside. When the water-soluble epoxy coating composition of the present invention is used for a base coat in a two-coating coating system, not only has excellent adhesion to the substrate, but also excellent adhesion to the top coat layer, so that excellent durability can be imparted to the coating film.

Hereinafter, the present invention will be described. However, it is not limited only by the following content, and each component may be variously modified or selectively used as necessary. Therefore, it is to be understood as including all changes, equivalents, and substitutes included in the spirit and scope of the present invention.

The water-soluble epoxy coating composition according to the present invention includes an epoxy resin, an amine or amide curing agent, and a silane compound. In addition, the water-soluble epoxy coating composition according to the present invention may further include a pigment, a solvent, and additives commonly used in the art, if necessary. Hereinafter, the composition of the water-soluble epoxy coating composition of the present invention is as follows.

Epoxy resin

The water-soluble coating composition according to the present invention contains an epoxy resin as a main resin. The epoxy resin is cured by reacting with a curing agent, and plays a role of securing adhesion to a substrate, water resistance, and corrosion resistance when forming a coating film.

The epoxy resin may include an epoxy resin having two or more, for example, 2 to 6 epoxy groups. The epoxy resin is not particularly limited as long as it is an epoxy resin having an epoxy group of 2 or more, but for example, bisphenol A type epoxy resin, ortho cresol novolac type epoxy resin, phenol aralkyl type epoxy resin, biphenyl type epoxy resin, multifunctional epoxy resin , Naphthalene-type epoxy resin and dicyclopentadiene-type epoxy resin may include one or more selected from the group consisting of.

The epoxy equivalent (EEW) of the epoxy resin is not particularly limited, but may be 800 to 1,500 g/eq (solution), for example, 900 to 1,200 g/eq (solution). In addition, the solid content may be 40 to 70%, for example 45 to 60% by weight, and the glass transition temperature may be -15 to 30 °C, for example -5 to 25 °C. When the epoxy equivalent, solid content, and glass transition temperature of the epoxy resin satisfy the above ranges, the degree of curing of the coating film may be improved.

The content of the epoxy resin is not particularly limited, but may be 15 to 60% by weight, for example, 20 to 50% by weight based on the total weight of the paint composition. If the content of the epoxy resin is less than 15% by weight, there may be problems with rust prevention and water resistance, and if it exceeds 60% by weight, reliability may decrease due to deterioration in curability and workability, and adhesion to the topcoat may be poor. .

Hardener

The water-soluble epoxy coating composition according to the present invention may include an amine curing agent or an amide curing agent as a curing agent, and in this case, it may provide excellent adhesion, low temperature drying, flexibility, rust prevention, and the like to the coating composition. In addition, the water-soluble epoxy coating composition of the present invention may include at least one of an epoxy-modified amine resin or an epoxy-modified amide resin as a curing agent, and in this case, drying and curing properties of the coating composition may be further improved.

As the epoxy-modified amine or amide, an epoxy adduct amine or amide may be used. Epoxy adduct amine or amide resin can be obtained by addition reaction of an epoxy resin and an amine compound or an amide compound, and the molecular weight of the epoxy resin is increased and thus volatility is suppressed, thereby providing a more stable curing reaction than when using an amine or amide curing agent. Can cause

As the epoxy resin, any epoxy resin known in the art may be used without particular limitation, and for example, a bisphenol A type epoxy resin or a bisphenol F type epoxy resin may be used. The epoxy equivalent of the epoxy resin may be 100 to 500 g/eq.

As the amine compound, for example, selected from the group consisting of butylamine, octylamine, diethylamine, dibutylamine, methylbutylamine, monoethanolamine, diethanolamine, N-methylethanolamine and diethylenetriamine More than one type can be used.

As the amide compound, for example, acrylamide, methacrylamide, N-methylol acrylamide, N-isopropyl acrylamide, diacetone acrylamide, N,N-methylene-bis-acrylamide, hydroxyalkylamide And one or more selected from the group consisting of fatty acid-modified amides may be used.

The active hydrogen equivalent of the amine or amide resin is 100 to 500 g/eq, for example, 150 to 300 g/eq, the glass transition temperature is -30 to 55°C, for example, 20 to 45°C, and the amine value is 100 to 450 The weight average molecular weight of mgKOH/g, for example 200 to 350 mgKOH/g, may be 500 to 4,500 g/mol, for example 1,500 to 3,500 g/mol. When the active hydrogen equivalent, glass transition temperature, amine value, and weight average molecular weight of the amine or amide resin satisfy the above ranges, excellent corrosion resistance can be secured.

The content of the amine or amide resin is not particularly limited, but may be 1 to 15% by weight, for example, 1 to 10% by weight based on the total weight of the coating composition. When the content of the amine or amide resin satisfies the above-described range, the degree of curing of the coating film is high, and physical properties of the coating film may be improved.

In the coating composition of the present invention, the main part and the curing agent part may be mixed so that the equivalent ratio (α) of the active hydrogen of the curing agent part to the epoxy group of the main part is 0.5 to 1.0, for example, 0.7 to 0.9. When the mixing ratio of the main part and the curing agent part satisfies the above-described range, the degree of curing of the coating film is increased, and at the same time, excellent adhesion, dryness, and rust resistance can be secured.

Silane compound

The water-soluble epoxy coating composition according to the present invention contains a silane compound. The silane serves to improve the degree of curing by increasing the crosslinking density of the epoxy resin, which is the main resin, and to improve the adhesion between the coating film formed by the epoxy coating composition and the object to be coated, and the interlayer adhesion between adjacent coating films in the multilayer coating film. Do it.

The kind of the silane compound is not particularly limited, but for example, silicic acid, tetramethoxysilane (TMOS), tetraethoxysilane (TEOS), methyltrimethoxy silane ), methyltriethoxy silane, vinyltrimethoxysilane, vinyltriethoxysilane, γ-(methacryloxypropyl)trimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ- Glycidoxypropylmethyldiethoxysilane, N-β(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxy Silane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, methyltrimethoxysilane and tris-[3-(trimethoxysilyl)propyl]isocyanate and trimethoxy[ At least one selected from the group consisting of 2-(7-oxabicyclo[4.1.0]hept-3-yl)ethyl]silane may be used.

The content of the silane compound is not particularly limited, but may be 0.05 to 10% by weight, for example, 0.1 to 5% by weight based on the total weight of the coating composition. When the content of the silane compound satisfies the above-described range, interlayer adhesion and substrate adhesion may be improved.

Pigment

The water-soluble epoxy coating composition of the present invention may further include a pigment. The pigment may include conventional extender pigments, colored pigments, rust inhibitors or mixtures thereof known in the art.

The extender pigment fills the pores in the coating film, complements the formation of the coating film, and plays a role of imparting rusting or mechanical properties to the coating film. Therefore, when the extender pigment is included, a good coating film appearance can be obtained, and hardness, impact resistance, and rust resistance can be improved. As the extender pigments, those commonly used in paint compositions may be used without limitation, and examples include calcium carbonate, clay, talc, magnesium silicate, kaolin, mica, silica, aluminum silicate, aluminum hydroxide, barium sulfate, and the like. . The above-described components may be used alone or two or more types may be used in combination.

Colored pigments can be used to express a desired color (color) in the paint or to increase the strength or gloss of the coating film. As such pigments, organic pigments, inorganic pigments, metallic pigments, aluminum-paste, pearl, etc., which are commonly used in paints, can be used without limitation, and these can be used alone or in combination of two or more. have. Non-limiting examples of color pigments that can be used include azo-based, phthalocyanine-based, iron oxide-based, cobalt-based, carbonate-based, sulfate-based, silicate-based, chromate-based pigments, and the like. Date, cyanine green, carbon black, iron oxide, sulfur iron oxide, navy blue, cyanine blue, and mixtures of two or more thereof.

The rust preventive pigment is a material introduced to improve corrosion resistance, and a conventional rust preventive pigment known in the art may be used. Non-limiting examples of rust-preventing pigments that can be used include zinc phosphate, silicate, aluminum zinc triphosphate, modified barium metaborate, zinc molybdate, calcium ion-substituted silica, and mixtures of two or more thereof.

The content of the pigment is not particularly limited, but may be 15 to 60% by weight, for example, 20 to 45% by weight based on the total weight of the paint composition. When the content of the pigment is in the above-described range, the color expression of the coating film is excellent, and mechanical properties, impact resistance, adhesion, etc. of the coating film may be improved.

solvent

The water-soluble epoxy coating composition according to the present invention contains water as a main solvent. Water, which is used as the main solvent, is a very important factor for the paint of the present invention to have eco-friendly properties. Water acts as a dispersion medium for each particle in the paint or a solvent for various compounds, and is also used as a diluent when added to the paint. In the present invention, pure water or deionized water may be used as water. In the present invention, water may be included in an amount of 10 to 40% by weight based on the total weight of the coating composition.

In addition, the water-soluble epoxy coating composition according to the present invention may further include an organic solvent in addition to water. As the organic solvent, a conventional organic solvent known in the art may be used without limitation, and for example, a hydrocarbon-based solvent, an ester-based solvent, an ether-based solvent, an alcohol-based solvent, or a mixture thereof may be used.

Non-limiting examples of usable organic solvents include cyclohexanone, xylene, toluene, cellosolve acetate, methyl ethyl ketone, dibasic ester, propylene glycol methyl ether acetate, n-butyl acetate, propylene glycol monomethyl acetate, 3-methoxy butyl acetate, ethylene glycol butyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol monobutyl ether, dipropylene glycol n-butyl ether, propylene glycol n-butyl ether, propylene glycol n- Propyl ether, ethanol, isopropanol, n-butanol, amyl alcohol, benzyl alcohol, or a mixed solvent thereof.

In the present invention, the content of the solvent may be a residual amount that satisfies the total weight of the coating composition (eg, 100% by weight), and may be, for example, 1 to 35% by weight based on the total weight of the coating composition. When the content of the solvent falls within the above-described range, workability is improved and excellent physical properties of the coating film can be exhibited.

additive

The water-soluble epoxy coating composition of the present invention may contain conventional additives known in the art within a range that does not impair the inherent properties of the composition.

Non-limiting examples of additives that can be used include dispersing agents, antifoaming agents, defoaming agents, leveling agents, plasticizers, curing accelerators, coloring agents, or mixtures thereof.

The dispersant plays a role of dispersing each material constituting the composition and preventing re-aggregation by maintaining a distance to express the uniform physical properties of the coating film. As the dispersant, conventional ones known in the art may be used. For example, a high molecular weight block copolymer type dispersant may be used.

The antifoaming agent serves to enhance the appearance of the coating film by suppressing air bubbles generated during coating, and conventional antifoaming agents known in the art may be used without limitation. For example, a silicone-based or non-silicone-based antifoaming agent may be used, and as an example, a polysiloxane type antifoaming agent may be used.

The thickener serves to control the viscosity and prevent precipitation, and conventional thickeners known in the art may be used without limitation. For example, the thickener may be silicate, magnesium, dichlorodimethylsilane, hydroxyethyl cellulose, urethane thickener, acrylic thickener, or the like.

The leveling agent is for improving the appearance properties of the coating film while improving adhesion in the composition by leveling the composition so that it is coated flat and smoothly. As the leveling agent, conventional ones known in the art may be used without limitation, and examples include acrylic, silicone, polyester, and amine leveling agents.

Plasticizers play a role in controlling the viscosity of the coating composition and improving storage stability. As the plasticizer, a conventional plasticizer known in the art may be used without limitation, and as an example, an aromatic ester plasticizer may be used.

The content of the additive may be appropriately adjusted within the content range known in the art, and for example, may be 0.1 to 20% by weight based on the total weight of the coating composition.

The water-soluble epoxy coating composition according to the present invention can be applied to a one-coating or two-coating coating system. For example, the water-soluble epoxy coating composition of the present invention may be used as a primer coating composition in a two-coating coating system. As the top coat composition, a water-soluble urethane paint composition, an acrylic emulsion paint composition, an aqueous polyurethane dispersion (PUD), an acrylic urethane aqueous dispersion (AUD), and the like may be used.

For example, the top coating composition may be a water-soluble urethane coating composition containing an acrylic polyol resin, a polyisocyanate, and a silane compound. The acrylic polyol resin has a weight average molecular weight of 20,000 to 80,000 g/mol. The hydroxyl value may be 50 to 250 mgKOH/g, the acid value may be 10 to 60 mgKOH/g, the glass transition temperature may be -5 to 60° C., and the solid content may be 20 to 60%. The isocyanate group content (NCO%) of the polyisocyanate may be 10 to 30% by weight based on the total weight of the curing agent. The equivalent ratio of the hydroxyl group (OH) of the acrylic polyol resin and the isocyanate group (NCO) of the polyisocyanate may be 1:0.6 to 1.6. In addition, the top coat composition may include 15 to 60% by weight of an acrylic polyol resin, 5 to 40% by weight of polyisocyanate, and 0.05 to 10% by weight of a silane compound based on the total weight of the top coat composition.

The present invention will be described in detail through the following examples. However, the following examples are only intended to aid understanding of the present invention, and the scope of the present invention is not limited to the examples in any sense.

[Example 1-9 and Comparative Example 1-2]

According to the composition shown in Table 1 below, an epoxy resin, a silane compound, a pigment, a solvent and an additive were mixed to prepare a main part, and a curing agent and a solvent were mixed according to the composition shown in Table 2 to prepare a curing agent part. Coating compositions of Examples 1-9 and 1-2 were prepared by mixing the main part and the curing agent part so that the equivalent ratio (α) of the active hydrogen of the curing agent part to the epoxy group of the main part was 0.8. The units used in Tables 1 and 2 are weight percent.

Epoxy resin 1: Epoxy equivalent 1,190 g/eq(solution), solid content 52%, glass transition temperature 25 ℃

Epoxy resin 2: Epoxy equivalent 800 g/eq (solution), solid content 57%, glass transition temperature 12 ℃

Epoxy resin 3: Epoxy equivalent 500 g/eq (solution), solid content 54%, glass transition temperature 15 ℃

Epoxy resin 4: Epoxy equivalent 1,650 g/eq(solution), solid content 55%, glass transition temperature 17 ℃

Epoxy adduct amine resin 1: active hydrogen equivalent 230 g/eq, glass transition temperature 35 ℃, amine value 255 mgKOH/g, weight average molecular weight 2,400 g/mol

Epoxy adduct amine resin 2: active hydrogen equivalent 150 g/eq, glass transition temperature 35 ℃, amine value 200 mgKOH/g, weight average molecular weight 3,000 g/mol

Epoxy adduct amine resin 3: active hydrogen equivalent 60 g/eq, glass transition temperature 35 ℃, amine value 400 mgKOH/g, weight average molecular weight 2,400 g/mol

Epoxy adduct amine resin 4: active hydrogen equivalent 550 g/eq, glass transition temperature 35 ℃, amine value 40 mgKOH/g, weight average molecular weight 5,400 g/mol

Amine resin: aliphatic amine resin (active hydrogen equivalent 284 g/eq, glass transition temperature 30°C, amine value 300 mgKOH/g, weight average molecular weight 3,000 g/mol)

Silane compound: trimethoxy[2-(7-oxabicyclo[4.1.0]hept-3-yl)ethyl]silane

Pigment 1: titanium dioxide (TiO ₂ )

Pigment 2: C.I pigment yellow (ferrous oxide)

Pigment 3: barium sulfate

Pigment 4: Talc

Pigment 5: Trizinc bis(orthophosphate)

Solvent 1: deionized water

Solvent 2: Diethylene glycol monobutyl ether

Additive 1: Antifoam (paraffin)

Additive 2: thickener (dichlorodimethylsilane)

Additive 3: Dispersant (High molecular weight block copolymer)

[Physical property evaluation]

After measuring the physical properties of the coating composition prepared according to Examples 1-9 and Comparative Example 1-2 as follows, the results are shown in Table 3 below.

Specimen preparation

80 to 90% by weight of the coating composition prepared according to Example 1-9 and Comparative Example 1-2 and 10 to 20% by weight of deionized water were mixed. After sanding the CR specimen, the mixture was coated with air spray (film thickness 50±5 μm). The specimen was left at room temperature for 20 minutes, cured at 80° C. for 30 minutes, and left at room temperature for 1 week to prepare a specimen.

Adherence

According to the ASTM D3359-02 evaluation standard, 100 squares were made by cross cut (1 mm), and the adhesion was evaluated based on the number of squares attached to the specimen when the tape was attached and removed.

Very Good: 100

Excellent: More than 70 and less than 100

Moderate: More than 50 and less than 70

Thirteen: less than 50

Curability

Using a drying timer recorder, WFT=125 μm, weight 100 g, and curability were evaluated at room temperature. It was evaluated relative to the touch drying in four stages of very good, excellent, fair and inferior.

Dryness

Using a drying timer recorder, dryness was evaluated under WFT=125 μm, weight 100 g, and room temperature conditions. It was evaluated relative to four stages of very good, excellent, moderate and poor by curing drying.

Water resistance

It was immersed at room temperature and constant water, and the appearance condition after 240 hours was evaluated.

Very good: no abnormality in appearance

Excellent: slight discoloration and gloss change

Moderate: severe discoloration and gloss change

Inferior: blisters and severe cosmetic changes

Anti-rust

According to ASTM D1654-92 evaluation criteria, one side generated after 5% NaCl SST (Salt Spray Test) was evaluated.

Very good: 1 mm or less on one side

Excellent: more than 1 mm on one side and 2 mm or less

Normal: More than 2 mm on one side and 3 mm or less

Inferior: more than 3 mm on one side

From the results of Table 3, the coating film formed of the coating composition of Example 1-9 according to the present invention was generally superior to the coating film formed of the coating composition of Comparative Example 1-2. In particular, it was confirmed that the coating film formed of the coating composition of Example 1-9 can reduce the content of volatile organic compounds and secure excellent adhesion, water resistance, and rust resistance.

Claims (8)

Epoxy resin;
Amine curing agents or amide curing agents; And
Water-soluble epoxy coating composition comprising a silane compound. The water-soluble epoxy coating composition of claim 1, wherein the epoxy resin has an epoxy equivalent of 800 to 1,500 g/eq, a solid content of 40 to 70%, and a glass transition temperature of -15 to 30°C. The water-soluble epoxy coating composition according to claim 1, wherein the curing agent is an epoxy adduct amine resin or an epoxy adduct amide resin. The method of claim 1, wherein the amine curing agent and the amide curing agent have an active hydrogen equivalent of 100 to 500 g/eq, a glass transition temperature of -30 to 55°C, an amine value of 100 to 450 mgKOH/g, and a weight average molecular weight of 500 to 4,500. Water-soluble epoxy coating composition in g/mol. The water-soluble epoxy coating composition according to claim 1, comprising 15 to 60% by weight of an epoxy resin, 1 to 15% by weight of an amine curing agent or an amide curing agent, and 0.05 to 10% by weight of a silane compound based on the total weight of the coating composition. A two-coat coating system comprising a primer coating composition and a top coating composition,
The primer coating composition is the water-soluble epoxy coating composition of claim 1,
The two-coating coating system wherein the top coat composition is at least one of a water-soluble urethane paint composition, an acrylic emulsion paint composition, an aqueous polyurethane dispersion (PUD), and an aqueous acrylic urethane dispersion (AUD). The two-coating coating system according to claim 6, wherein the water-soluble urethane coating composition comprises an acrylic polyol resin, a polyisocyanate, and a silane compound. The method of claim 7, wherein the acrylic polyol resin has a weight average molecular weight of 20,000 to 80,000 g/mol. A two-coating coating system having a hydroxyl value of 50 to 250 mgKOH/g, an acid value of 10 to 60 mgKOH/g, a glass transition temperature of -5 to 60° C., and a solid content of 20 to 60%.