KR100195759B1 - Organic-inorganic composite metal surface coating composition for zinc plated steel - Google Patents

Abstract

A water-soluble thin film type organic-inorganic composite coating composition for galvanized steel sheet having excellent properties including low temperature curing ability and considering environmental and energy problems is disclosed. The composition is composed of 100 parts by weight of an acrylic or vinyl modified epoxy resin which is a water-soluble organic polymer resin, 5-100 parts by weight of a silica-based inorganic compound, and 1 to 50 parts by weight of a curing agent by the solid content ratio of the water-soluble organic polymer resin. When forming a thin film coating film on a galvanized steel sheet, it is excellent in low-temperature hardening ability, and is excellent in alkali resistance, corrosion resistance, base material adhesion, electrodeposition coating property, powder resistance, continuous welding property, and painting work ability. In addition, the use of acryl or vinyl-based modified epoxy resins as a main raw material reduces energy saving problems, environmental pollution problems, work hygiene stability and fire risk.

Description

Organic-Inorganic Composite Metal Surface Coating Composition

The present invention relates to an organic-inorganic composite metal surface coating composition for galvanized steel sheet. More specifically, the present invention relates to a composition of an organic-inorganic composite metal surface coating agent which greatly improves the surface protection ability and the corrosion resistance of a zinc plated steel sheet. The present invention is invented by the inventors and dated December 10, 1996, the organic-inorganic composite metal surface coating for zinc alloy plating of Patent Application No. 96-63879 entitled Organic-Inorganic Composite Metal Surface Coating Composition. An improved invention of the replication composition.

Conventionally, research efforts have been made to improve the performance of corrosion-resistant steel sheets using alloy techniques using metals such as zinc, nickel, chromium, manganese, aluminum, copper, cobalt, and the like. However, it was difficult to obtain sufficient corrosion resistance, and steel sheets such as stainless steel sheets having excellent corrosion resistance are very expensive and their use is limited. In addition, in North America and Europe, a large amount of deicing and deicing salts are used in order to prevent winter freezing, and thus, in the case of corrosion resistant steel sheets for automobiles, the rust prevention standards of automobiles have become very strict. As a method of solving these problems, a method of using an organic coating has been proposed. As a conventional organic coating agent for corrosion-resistant steel sheet, although the thick film type organic coating agent which coats a film about 15 microns is used, there exist problems, such as powdering, continuous weldability, sacrificial anticorrosion ability, etc. at the time of shaping | molding process.

Recently, a thin film composite coating material having a thickness of 1 to 2 microns has been developed. These thin film composite coatings not only have excellent corrosion resistance, but also have improved properties such as continuous workability, powder resistance, electrodeposition paintability, and the like than the thick film organic coating.

Thin film type organic-inorganic composite surface coating agent is mainly applied to zinc alloy plated steel plate plated with alloy such as zinc-nickel. As a coating method, 20-100 mg / m ² of chromium or phosphoric acid is mainly coated on zinc alloy plated steel plate. After coating a chromium-free surface treatment agent, the coating method is used to coat the substrate at 5 microns or less and continuously apply-cure and dry the material temperature (MT) at 100-250 ° C.

In conventional thin film composite coatings, epoxy resins, acrylic resins, urethane resins or modified epoxy resins, modified acrylic resins, and the like are used as resins (binders), but these include adhesion to materials, curability, corrosion resistance, continuous weldability, It has the defects of powder resistance, alkali resistance, and electrodeposition performance. In particular, the high curing temperature of 200 ℃ is recognized as a big problem not only in the energy efficiency problems but also in the performance of high tensile steel sheet.

In addition, in the case where the coating material of the thin film is not sufficiently cured, an alkali degreasing process performed during the post-processing process, the coating film is peeled off during the washing process, or the pretreated chromium solution is eluted, which greatly reduces the corrosion resistance of the steel sheet or causes important environmental problems. You can.

Accordingly, the present inventors have continued their research efforts to improve the defects of the conventional thin film composite coatings and to develop a thin film composite coating composition which can be used in zinc alloy plated steel sheets plated with an alloy such as zinc-nickel. Acryl or vinyl-based modified epoxy resin with excellent low temperature curing ability, excellent alkali resistance, corrosion resistance, substrate adhesion, electrodeposition paintability, powder resistance, continuous weldability, and painting work ability and applicable to galvanized steel Water-soluble thin film organic-inorganic composite coating composition was developed in consideration of energy and environmental issues, and was filed on December 10, 1996 with the application of the patent of organic-inorganic composite metal surface coating composition. Application No. 96-63879 is currently pending with the Patent Office.

The present inventors continue their research efforts to apply the above-described organic-inorganic composite metal surface coating composition to a zinc plated steel sheet plated with zinc, which is relatively inexpensive than a zinc alloy plated steel sheet plated with an alloy such as zinc-nickel. As a result, even when the organic-inorganic composite metal surface coating composition having the above composition is applied to a galvanized steel sheet, it has been found to be excellent in various properties including low temperature curing ability, thereby completing the present invention.

Accordingly, an object of the present invention is to provide a water-soluble thin film type organic-inorganic composite coating composition having excellent properties including low temperature hardening ability in a galvanized steel sheet and considering environmental and energy issues.

In order to achieve the above object, the present invention is a zinc plating consisting of 100 parts by weight of an acrylic or vinyl-modified water-soluble organic polymer resin, 5-100 parts by weight of a silica-based inorganic compound and 1 to 50 parts by weight of a curing agent by the solid content of the water-soluble organic polymer resin. An organic-inorganic composite coating composition for steel sheet is provided.

The organic-inorganic composite coating composition according to the present invention contains a water-soluble organic polymer resin, a silica-based inorganic compound, and a curing agent as main components. In addition to the above-described main component, it may further include an additive for adjusting the solution performance.

The water-soluble organic polymer resin is a water-soluble resin that uses an acrylic or vinyl-modified epoxy resin as a main raw material, minimizes energy saving, environmental pollution, work hygiene safety, fire risk.

The main component of the water-soluble organic polymer resin is composed of an epoxy resin and an acryl or vinyl material. The epoxy resin preferably has a molecular weight of 350-7000 and an epoxy equivalent of 150-3000. When molecular weight is less than 350, peeling of a cured coating film becomes a problem, and when molecular weight is 7000 or more, a modification reaction and water solubility become difficult. In order to adjust molecular weight and epoxy equivalent weight, bisphenol may be added and reacted from a low molecular weight liquid epoxy resin to adjust molecular weight. Representative epoxy resins include bisphenol-A, bisphenol-F, and novolac epoxy resins.

In order to reduce the glass transition temperature (Tg) of the epoxy resin to improve the flexibility of the coating film, and to improve the adhesion and coating workability to the plating material, the growth reaction of the aliphatic compound of the dibasic acid system, the fatty acid of the monofunctional group and the monofunctional group is stopped. You can also use the agent.

The use of the raw materials may be used alone or mixed with a dibasic acid-based aliphatic compound, a monofunctional fatty acid and a monofunctional growth stopper (Chain Stopper), respectively. It is preferable that these usage-amounts are 5-200 weight part with respect to 100 weight part of epoxy resins. If the amount thereof is less than 5 parts by weight based on 100 parts by weight of the epoxy resin, there is a risk of gelation due to a rapid reaction. If the amount is more than 200 parts by weight, the molecular weight is too small, which is not preferable. As a typical dibasic acid aliphatic compound, adipic acid, aziraic acid, the dimer acid which is a tall oil fatty acid polymer, etc. are mentioned. Examples of the monofunctional fatty acid include coconut oil fatty acid, cottonseed oil fatty acid, dehydrated castor oil fatty acid, linseed oil fatty acid, soybean oil fatty acid, tall oil fatty acid, pelagonic acid, oleic acid and linoleic acid.

Examples of the growth reaction terminator of the monofunctional group include benzoic acid, para-benzoic acid (p-tertiary) and the like. The modification of the acrylic or vinyl compound (monomer) to the epoxy resin may be carried out by using a graft polymerization method on the epoxy resin together with the reaction catalyst or by a polymerization method using an unsaturated acid such as maleic acid or fumaric acid. Can be. It is preferable that these usage amounts are 10-100 weight part of an acryl or vinylic monomer with respect to 100 weight part of epoxy resins. If the amount of use is less than 10 parts by weight, the modification effect cannot be sufficiently exhibited. If the amount is more than 100 parts by weight, the powdering resistance and the corrosion resistance decrease rapidly, which is not preferable.

Representative acrylic or vinyl monomers that may be used in the present invention are as follows. Nonfunctional monomers include methyl acrylate, ethyl acrylate, isopropyl acrylate, N-butyl acrylate, ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, hexyl methacrylate, Lauryl methacrylate, and the like. Acrylic acid, methacrylic acid, maleic acid, itaconic acid, croronic acid, etc. are mentioned as a monomer which has a carboxyl functional group. As monomers having a hydroxyl group, 2-hydroxy methacrylate, hydroxypropyl acrylate, 2-hydroxyethyl acrylate, acrylamide, N-methylol acrylamide, glycidyl methacrylate, styrene, vinyl toluene , Acrylonitrile, vinyl acetate, and the like. It is preferable to use a well-known peroxide type catalyst generally as a reaction catalyst.

As a technical method for accommodating an epoxy resin in which an acryl-based or vinyl-based compound is modified, a method of hydrophilizing a part of a polymer by using a neutralizing agent that ionizes and charges the resin may be mentioned. The ionized ion resins are classified into anionic resins, cationic resins, and nonionic resins. Cationic resins are acidic in nature, and their use is limited because they easily corrode containers and equipment. In the case of anionic resins, since the solution used is alkaline, there are few restrictions on the equipment, and thus they are generally widely used. As a typical hydrophilic functional group of the anionic resin, a carboxyl group is used.

As a method of introducing a carboxyl hydrophilic group into an epoxy resin modified with an acrylic or vinyl compound, in the presence of a catalyst using a raw material having an unsaturated functional group such as maleic acid, fumaric acid, croronic acid, acrylic acid, methacrylic acid, etc. It is copolymerized with an acrylic or vinyl modifier. It is preferable that the acid value of resin is 20-200 mg KOH / g. When the acid value of the resin is less than 20 mg KOH / g, it is difficult to solubilize, and when the acid value of the resin is larger than 200 mg KOH / g, the corrosion resistance and water resistance is sharply lowered. Preference is given to using neutralizing agents of amines or alkali metals in order to neutralize and accept the carboxyl groups.

As silica type inorganic compounds used for the organic-inorganic composite metal surface coating agent of this invention, dry silica, colloidal silica, etc. are mentioned. The metal alloy steel plate with silica added exhibits excellent corrosion resistance under repeated wet and dry conditions.

Dry silica has a rough surface roughness and a marked decrease in gloss, resulting in poor surface appearance. Therefore, it is preferable to use colloidal silica. Colloidal silica may be an acidic solution having a particle size of 5-200 nm and having a pH of 2 to 4 or an alkaline solution having a pH of 8-10.5. The amount of colloidal silica is preferably used in the amount of 5-100 parts by weight based on 100 parts by weight of the water-soluble organic polymer resin. If the amount is less than 5 parts by weight, the corrosion resistance is lowered. If the amount is more than 100 parts by weight, the viscosity of the solution rises rapidly during storage and the workability is significantly reduced.

The curing agent of the organic-inorganic composite metal surface coating agent is an important factor that primarily determines the electrodeposition workability of the coating agent, alkali resistance, and the curing property of the coating agent which prevents elution of the chromium-based surface treatment agent to water.

Examples of the raw material which can be used as a curing agent include melamine-formaldehyde resins, urea-formaldehyde resins, and benzoguanimine-formaldehyde resins as amino resins. It is preferred to use isocyanates. It is effective to use an alcohol-based or oxime-based blocking agent capable of dissociating at a low temperature. It is preferable to use 1-50 weight part of hardening | curing agents by solid content with respect to 100 weight part of water-soluble organic polymer resins when using an amino-type hardening | curing agent or a blocked isocyanate hardening | curing agent. When the amount of the curing agent used is less than 1 part by weight, the curability becomes poor, which is problematic for alkali resistance, solvent resistance, and the like. When the amount of the curing agent is greater than 50 parts by weight, brittleness occurs and the material adhesion and the powdering resistance deteriorate.

As the additive of the organic-inorganic composite coating agent, an anti-foaming agent for adjusting the bubble of the solution, a surface tension regulator for the surface and workability, an antirust coating agent, an isocyanate blocking agent, a catalyst for dissociation and curing, and the like can be used.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples, and the present invention is within the spirit and scope of the present invention based on the detailed description of the present invention and the claims. It will be appreciated that various modifications and applications are possible within the scope of the present invention.

Synthesis Example 1

153.3 parts by weight of a resin having a bisphenol-based epoxy equivalent of 750-2100, 53.1 parts by weight of dimeric acid (87% of dimer, 13% of trimer) and 35.1 parts by weight of soybean oil fatty acid, with a condenser equipped with a stirrer, a heater, a thermometer and a decanter. Into a four-necked flask, the temperature was gradually raised to 230 to 250 ° C and allowed to react so that the acid value was 5 or less. The reaction was diluted with 75 parts by weight of butyl cellosolve at a temperature of no greater than 150 ° C.

To the resultant, 17.2 parts by weight of methacrylic acid, 24.1 parts by weight of 2-hydroxyethyl methacrylate, 35.2 parts by weight of butyl methacrylate, 21.2 parts by weight of styrene, and 43 parts by weight of cumene hydroperoxide as an initiator were added dropwise at 130 ° C for 3 hours. The reaction was carried out so that the residual monomer was less than 0.5%. Next, the resultant was cooled to a temperature of 70 ° C. or lower, and neutralized by adding 20.3 parts by weight of dimethylethanolamine, and 1100 parts by weight of water was added to give a clear solid having a solid content of 22%, pH 8.5, and viscosity of 14 seconds (4 cups 20 ° C.). A milky white solution was obtained.

Synthesis Example 2

200 parts by weight of a bisphenol epoxy (molecular weight 1400) resin and 168 parts by weight of dimer acid were placed in a 2 L four-necked flask equipped with a stirrer, a heater, a thermometer, and a condenser, and the reaction mixture was heated to 210 ° C to have an acid value of 30-35. After cooling the resultant to 100 ℃, 9.9 parts by weight of maleic anhydride was added and reacted for 30-60 minutes at 100 ℃ to give a final acid value of 40-45. Next, 30 parts by weight of triethylamine was added to the resultant at 70 ° C. or less, stirred for 10 minutes, and then 1480 parts by weight of water was added and stirred at a speed of 300 rpm to prepare a milky transparent aqueous solution having a solid content of 20% and a pH of 8.5. .

Example 1

100 parts by weight of the milky white solution obtained in Synthesis Example 1, 42.8 parts by weight of silica sol (Snowtex C solid content made by Nippon Ilsan Chemical Co., Ltd.), 7.9 parts by weight of Cymel 303 (trade name; manufactured by American Cinnamid, Inc.), BW Kay as an antifoaming agent. 0.2 parts by weight of 023 (manufactured by BEIKA, Germany), 0.5 parts by weight of a 6% solution of cobalt octane, and 72 parts by weight of water to obtain an organic-inorganic composite coating composition having a solid content of 15-16% and a pH of 8.5 to 9. It was.

Example 2

100 parts by weight of the milky white solution obtained in Synthesis Example 1, 42.8 parts by weight of silica sol (Snowtex C solid content of Nippon Ilsan Chemical Co., Ltd.), 17.8 parts by weight of blocked isocyanate having 40% solids, BWK 023 as a defoamer (Buyei, Germany) Manufactured by Caesar) organic-inorganic having a solid content of 15-16% and a pH of 8.5 to 9 by mixing 0.2 parts by weight, 2.0 parts by weight of a tin compound in a 20% aqueous dispersion solution, 1.0 part by weight of a 1% aqueous acetate solution, and 62.5 parts by weight of water. A composite coating composition was obtained.

Example 3

100 parts by weight of the milky white solution obtained in Synthesis Example 1, 42.8 parts by weight of silica sol (Snowtex O solids, manufactured by Nippon Ilsan Chemical Co., Ltd.), 17.8 parts by weight of blocked isocyanate having 40% solids, BWK 023 (defoamer, Germany) Manufactured by Caesar) organic-inorganic having a solid content of 15-16% and a pH of 7.5 to 8 by mixing 0.2 parts by weight, 2.0 parts by weight of a tin compound in a 20% aqueous dispersion solution, 1.0 part by weight of a 1% aqueous solution of acetate, and 62.5 parts by weight of water. A composite coating composition was obtained.

Comparative Example 1

100 parts by weight of the milky white solution obtained in Synthesis Example 2, 42.8 parts by weight of silica sol (Snowtex C solid content of Nippon Ilsan Chemical Co., Ltd.), 17.8 parts by weight of blocked isocyanate having a solid content of 40%, BWK 023 (foam agent) Manufactured by Caesar) organic-inorganic having a solid content of 15-16% and a pH of 8.5 to 9 by mixing 0.2 parts by weight, 2.0 parts by weight of a tin compound in a 20% aqueous dispersion solution, 1.0 part by weight of a 1% aqueous acetate solution, and 62.5 parts by weight of water. A composite coating composition was obtained.

Comparative Example 2

100 parts by weight of the milky white solution obtained in Synthesis Example 2, 42.8 parts by weight of silica sol (Snowtex C solid content made by Nippon Ilsan Chemical Co., Ltd.), 7.9 parts by weight of Cymel 303 (trade name), and BK Kay 023 (Buyay Kay, Germany) Product) 0.2 parts by weight, 0.5 parts by weight of a 6% solution of cobalt octet, and 72 parts by weight of water were obtained to obtain an organic-inorganic composite coating composition having a solid content of 15-16% and a pH of 8.5 to 9.

[Production of Psalms]

The coating composition obtained in Examples 1 to 3 and Comparative Examples 1 and 2 was coated on a 1 ton galvanized 20-30 mg / m ² steel plate treated with 50 mg / m ^{2 of} chromium by using a bar coater No. 3 It was applied to a micron and dried in a forced hot air circulation oven so that the body surface temperature was 180 ° C.

[Test Specimen]

[Exterior test]

It was visually observed whether the appearance of the coated specimen was good without foreign matter, stains and unpainted parts.

Electrodeposition paintability (cationic electrodeposition) test

After electrodeposition coating at low voltage (30-50V) and high voltage (200-230V), the surface appearance, pinhole, linearity, glossiness and roughness were evaluated.

[Alkali Resistance (5% NaOH 5min) Test]

After treatment with 5% aqueous NaOH solution or phosphate, the surface was visually observed and the color difference was measured to evaluate the value of ΔE.

[Solvent resistance (MEK reciprocating rubbing)]

Methyl ethylene ketone (MEK) was buried in the gauze and reciprocated rubbing with a constant force to observe the coating state.

Corrosion Resistance Test

1. Plates and processing specimens were tested for Salt Spray Test (SST) and Cyclic Corrosion Test (CCT) for 5% saline at 36 ℃ for 4 hours, drying at 60 ℃ for 2 hours, 95% RH 50 It evaluated on the conditions of 2 degreeC.

2. After electrodeposition coating, after mid-medium phase treatment, incision was made by X to observe the progress of blister width in CCT.

[Continuous weldability test (5000 times)]

Appropriate current range and continuous RBI were evaluated.

[Chrome Dissolution Test]

After the specimen was immersed in water at 25 ° C. for 24 hours, chromium elution was confirmed by ICP (Inorganic Analyzer).

[Powdering test]

After 20% tensile, after peeling with paper, powdering was evaluated.

The coating film test results of the specimens are shown in Table 1 below.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Exterior ◎ ◎ ◎ ○ ○ Electrodeposition paintability △ ◎ ◎ ◎ △ Alkali resistance △ ◎ ◎ ◎ △ Solvent resistance ○ ○ ○ ○ X Corrosion resistance ○ ◎ ◎ X X Continuous weldability ○ ◎ ◎ △ △ Elution ○ ◎ ◎ ◎ △ Powdering property ○ ○ ○ ○ ○

Evaluation: ◎ Best, ○ Excellent, △ Normal, X Poor

As can be seen in Table 1, when forming a thin film coating on a galvanized steel sheet using an organic-inorganic composite coating composition using an acrylic or vinyl-based water-soluble organic polymer resin according to the present invention, low-temperature curing ability It is excellent in alkali resistance, corrosion resistance, base material adhesion, electrodeposition coating resistance, powder resistance, continuous welding resistance, coating work ability is excellent. In addition, the use of water-soluble acrylic or vinyl-based modified epoxy resin as the main raw material minimizes energy saving problems, environmental pollution problems, work hygiene stability and fire risk.

On the other hand, when forming a thin film coating film on a steel plate using the conventional bisphenol-type epoxy resin, not only solvent resistance, corrosion resistance, and continuous weldability were bad, but also it was inferior to the coating composition of this invention from an external viewpoint.

As described above, in the case of forming a thin film coating on a galvanized steel sheet using an organic-inorganic composite coating composition using an acrylic or vinyl-based water-soluble organic polymer resin, it has excellent low-temperature curing ability, alkali resistance, corrosion resistance, Excellent adhesiveness, electrodeposition paintability, powder resistance, continuous weldability, and painting work ability. In addition, the use of an acryl or vinyl-based modified epoxy resin as a main raw material reduces energy saving problems, environmental pollution problems, work hygiene stability and fire risk.

Claims (7)

An organic-inorganic composite coating composition for galvanized steel sheet comprising 100 parts by weight of an acryl or vinyl-modified water-soluble organic polymer resin, 5-100 parts by weight of a silica-based inorganic compound, and 1 to 50 parts by weight of a curing agent by solid content of the water-soluble organic polymer resin. The organic-inorganic composite coating composition for galvanized steel sheet according to claim 1, wherein the water-soluble organic polymer resin is a bisphenol epoxy resin having a molecular weight of 350-7,000 and an epoxy equivalent of 150-3,000. The dibasic acid-based aliphatic compound and monofunctional group according to claim 2, in order to reduce the glass transition temperature (Tg) of the bisphenol-based epoxy resin to improve the flexibility of the coating film and to improve adhesion to the plating material and coating workability. The organic-inorganic composite coating composition for galvanized steel sheet further comprising 5-200 parts by weight based on 100 parts by weight of the bisphenol-based epoxy resin alone or in combination with a fatty acid and a monofunctional growth inhibitor. The method of claim 1, wherein the acrylic or vinyl-modified epoxy resin is carried out by using a graft polymerization method using 10-100 parts by weight of an acryl or vinyl-based monomer to 100 parts by weight of an epoxy resin together with a reaction catalyst. Or an organic-inorganic composite coating composition for galvanized steel sheet, which is obtained by a polymerization method using unsaturated acid. The method of claim 1, wherein the acryl or vinyl monomers are methyl acrylate, ethyl acrylate, isopropyl acrylate, N-butyl acrylate, ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate. Non-functional monomers consisting of latex, hexyl methacrylate and lauryl methacrylate, monomers with carboxyl functional groups consisting of acetic acid methacrylic acid, maleic acid, itaconic acid and croronic acid, and 2-hydroxymethacryl Having a hydroxyl group consisting of latex, hydroxypropyl acrylate, 2-hydroxyethyl acrylate, acrylamides, N-methylol acrylamide, glycidyl methacrylate, styrene, vinyltoluene, acrylonitrile and vinyl acetate At least one selected from the group consisting of monomers Organic-inorganic composite coating composition for mild plated steel sheet. The organic-inorganic composite coating composition for galvanized steel sheet according to claim 1, wherein the silica-based inorganic compound is colloidal silica having a particle size of 5-200 nm. The method of claim 1, wherein the curing agent is an organic resin for galvanized steel sheet or blocked isocyanate selected from the group consisting of melamine-formaldehyde resin, urea-formaldehyde resin and benzoguanamine-formaldehyde resin Inorganic composite coating composition.