KR20030021774A - Coating compositions for gavanized steel sheets and gavanized steel sheets treated with them - Google Patents

Abstract

PURPOSE: A surface treatment composition for galvanized steel sheet having superior corrosion resistance, coherence property and low temperature drying property, and the galvanized steel sheet treated with the surface treatment composition are provided. CONSTITUTION: The surface treatment composition for galvanized steel sheet comprises 80 to 50 wt.% of a mixed resin in which aqueous organic resin and inorganic component are mixed in a solid ratio of 70:30 to 30:70, 10 to 40 wt.% of phosphate based corrosion resistance rust inhibitor of metal oxides and 1 to 20 wt.% of organic metal complex compound by solid mass of the surface treatment composition for the galvanized steel sheet, wherein the aqueous organic resin is selected from aqueous or water dispersed acrylic polymer resin having hydroxyl group or carboxyl group, epoxy resin, or a mixture thereof, the inorganic component is selected from alumina sol, silica sol, titania sol, zirconia sol, or a mixture thereof, the phosphate based corrosion resistance rust inhibitor of metal oxides is selected from phosphate solution of aluminum, aluminum polyphosphate, manganese, zinc, molybdenum and fluorine, phosphate solution of hexaammonium heptamolybdate tetrahydrate, phosphate solution of soda, or a mixture thereof, and the organic metal complex compound is selected from silane based coupling agent, titanium based coupling agent, zirconium based coupling agent, or a mixture thereof.

Description

Surface treatment composition for galvanized steel sheet and galvanized steel sheet treated using the same {Coating compositions for gavanized steel sheets and gavanized steel sheets treated with them}

The present invention relates to a surface treatment composition for galvanized steel sheet and a galvanized steel sheet treated using the same. More specifically, the present invention relates to a surface treatment composition for galvanized steel sheet excellent in corrosion resistance, paintability and low temperature drying property, and a galvanized steel sheet treated using the same.

In order to add corrosion resistance and special functions to the cold rolled steel sheet, the steel sheet is plated with zinc and various metals to manufacture galvanized steel sheets and various plated steel sheets. However, in such a galvanized steel sheet and various coated steel sheets, rust such as white rust occurs as metal components such as zinc are exposed to a corrosive environment for a long time.

Therefore, in order to prevent the occurrence of white rust, such as galvanized steel sheet, surface treatment using a pretreatment agent, such as inorganic phosphate type and chromate type, has been performed conventionally. Among them, chromate pretreatment has been used as the most excellent in terms of corrosion resistance and economical. That is, chromate prevents oxidation of iron and zinc due to the strong self-oxidizing ability of chromium 6+ and thus increases corrosion resistance of the steel sheet. In addition, chromate treatment has been widely used in the industry as a very economical because of the low processing cost.

However, in recent years, as the seriousness of health and safety and environmental pollution and the demand for environmental regulations have increased, restrictions on the use of harmful ingredients are increasing.

Chromic acid may cause lung cancer to workers due to the strong oxidizing power of chromic acid in the pretreatment process of the steel sheet using the same, and also cause serious water pollution when the wastewater generated in the treatment process is released, and thus, wastewater treatment cost This is caused excessively.

Therefore, after 2003, in Europe, the use of hexavalent chromium-containing steel sheet is regulated in automobile vehicles, and pre-treatment products containing no chromium are introduced in the home appliance field.

In this regard, while researches on products that satisfy the workability and economic efficiency while retaining the corrosion resistance of the existing chromium, the technologies currently being developed do not exhibit sufficient corrosion resistance effect of chromate treatment, Effects of lower limbs are also insignificant.

In addition, since a very high temperature of about 150 ~ 230 ℃ PMT is required during drying, it is often impossible to apply it directly to the pretreatment line of the existing chromate system, and the economical cost increases significantly and it is difficult to put it to practical use.

3+ chromium, which is relatively harmful to the environment and human body, is mixed with other acidic materials to prepare a steel sheet surface treatment agent. However, this too is harmful to contain chromium.

In addition, various techniques such as coating using molybdate, which forms an oxide on the surface, a method of forming hydrated cerium oxide on the surface of a steel sheet using a rare earth metal salt such as CeCl 3, thioglycolate, and alkoxide coating have been studied.

However, these products have a large difference in physical properties according to drying conditions, the drying temperature should be very high, such as PMT 150 ~ 200 ℃, there is a problem that the treatment time of the treatment agent is also deposited in a few minutes to a few minutes.

In addition, acid treating agents based on inorganic acids such as hexafluorozirconic acid and hexafluorosalicylic acid are used. However, when the steel sheet is treated using the same, the surface and appearance of the steel sheet are severely affected depending on the processing temperature and time. It is different and the work is very difficult.

It is an object of the present invention to provide an environmentally friendly and harmless surface treatment composition for galvanized steel sheet.

Another object of the present invention is to provide a surface treatment composition for galvanized steel sheet excellent in corrosion resistance and coating film adhesion.

Still another object of the present invention is to provide a galvanized steel sheet treated using the surface treatment composition for galvanized steel sheet of the present invention.

According to one aspect of the invention,

80 to 50% by weight of the mixed resin in which the water-soluble organic resin and the inorganic component are mixed in the solid content ratio of 70:30 to 30:70, 10 to 40% by weight of the phosphate-based corrosion-resistant rust inhibitor of metal oxide, and organic It comprises 1 to 20% by weight of the metal complex,

As the water-soluble organic resin, a water-soluble or water-dispersible acrylic resin and an epoxy resin having a hydroxyl group or a carboxyl group are used alone or in a mixture of two or more,

As the inorganic component, alumina sol, silica sol, titania sol, zirconia sol is used alone or a mixture of two or more thereof,

The phosphate-based corrosion-resistant rust inhibitor of the metal oxide is aluminum, aluminum phosphate, manganese, zinc, molybdenum, phosphate solution of fluorine, phosphate solution of hexaammonium hepta molybdate tetra hydrate and phosphate solution of soda alone or a mixture of two or more Is used,

The organometallic complex is provided with a surface treatment composition for galvanized steel sheet in which a silane coupling agent, a titanium coupling agent and a zirconium coupling agent are used alone or in a mixture of two or more thereof.

According to another aspect of the present invention,

Provided is a galvanized steel sheet in which the surface treatment composition for galvanized steel sheet according to the present invention is treated with a dry deposition amount of 300 to 1000 mg / m 2.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The treated composition for galvanized steel sheet of the present invention does not contain chromium and is environmentally friendly and harmless to humans. In addition, when the galvanized steel sheet is treated with the steel sheet surface treatment composition of the present invention, corrosion resistance and coating film adhesion property equivalent to those when treated with a chromium-based treatment composition used conventionally are exhibited. Further, after coating the surface treatment composition on a steel sheet, it is possible to dry at a low temperature of PMT 80 ~ 130 ℃.

The zinc-plated surface treatment composition of the present invention uses a mixture of an organic resin and an inorganic component to express the advantages of the organic resin and the inorganic resin. In the present invention, the organic resin and the inorganic resin are mixed in a solid ratio of 70:30 to 30:70, which is hereinafter referred to as 'mixed resin'.

As the water-soluble organic resin, a water-soluble or water-dispersible acrylic resin and an epoxy resin having a hydroxyl group or a carboxyl group may be used alone or in a mixture of two or more.

As the inorganic component to impart corrosion resistance, metal sol such as alumina sol, silica sol, titania sol, zirconia sol and the like may be used alone or in a mixture of two or more. Generally, an inorganic metal sol having a particle size of 50 to 700 nm may be used. When the inorganic particles exceed 700 nm, defects occur on the surface of the film during film formation, and the smaller the better, the less economical.

The mixed resin in which the water-soluble organic resin and the inorganic component are mixed in the solid content ratio of 70:30 to 30:70 is contained in 50 to 80% by weight based on the weight of the solid of the surface treatment composition.

When the ratio of the water-soluble organic resin to the inorganic component exceeds 70% by weight, the effect of improving the corrosion resistance by the inorganic sol is insufficient, and when less than 30% by weight, the effect of forming a uniform film by the aqueous organic resin is reduced. Further, the mixed resin is included in the 50 to 80% by weight based on the weight of the surface treatment composition solids in consideration of the volume stability coating workability, coating thickness and other physical properties of the surface treatment composition.

Corrosion-resistant rust inhibitors are selected in consideration of compatibility with them, depending on the water-soluble organic resin and inorganic components used. In the present invention, a phosphate-based corrosion-resistant corrosion inhibitor of a metal oxide is used, for example, phosphate solution of aluminum, aluminum phosphate, manganese, zinc, molybdenum, fluorine, phosphate aqueous solution of hexaammonium hepta molybdate tetrahydrate, phosphate of soda A solution is mentioned. Such corrosion resistant rust inhibitors may be used in one or two or more mixtures. Furthermore, the phosphate solution may be used by adding up to 15% by weight, based on the weight of the surface treatment composition solids, as a stabilizer to minimize the change in viscosity and pH in the phosphate solution over time and to prevent precipitation.

The corrosion-resistant rust inhibitor may be added in 10 to 40% by weight based on the solids weight of the surface treatment composition. If the added amount of the anticorrosive rust preventive agent is less than 10% by weight, the intended corrosion resistance is not sufficiently exhibited. If the amount of the anticorrosive anticorrosive agent is more than 40% by weight, it is not preferable for continuous film formation, and the storage stability of the solution may also be lowered.

Furthermore, organometallic complexes are used to further improve corrosion resistance and adhesion with the steel sheet. The organometallic complex compound provides the adhesion of the surface treatment composition to the galvanized steel sheet by the coupling reaction with the galvanized steel sheet, not only increases the corrosion resistance of the steel sheet, but also imparts the coating baseability. The organometallic complex may be added in an amount of 1 to 20% by weight based on the weight of the treated composition. If it is added less than 1% by weight, the effect of the addition of the organometallic complex is insignificant, and if it exceeds 20% by weight, it is uneconomical and the stability of the treated composition is lowered.

As the organometallic complex, a silane coupling agent, a titanium coupling agent and a zirconium coupling agent may be used alone or in a mixture of two or more.

As the silane coupling agent, vinyl trichlorosilane, vinyl triethoxysilane, vinyl trimethoxysilane, 3-methacryloxypropyl trimethoxysilane, 2-glycosyl propyltrimethoxysilane, 3-glysiloxy Propyl methyldimethoxysilane, 3-glycyoxypropyl methyldiethoxysilane, N-2- (aminoethyl) -3-aminopropyl triethoxysilane, 4-aminopropyl triethoxysilane, N-phenol-3- Aminopropyl trimethoxysilane, 3-ureido alkyl triethoxy silane and the like can be used.

Titanium-based coupling agents include titanium stearate complex, organic titanium phosphate complex, titanium acetyl acetonate, iso-butoxy titanium ethyl aceto acetate, di-iso-propoxy titanium bis ethylacetoacetate, tetra isopropyl titanate, tetra normal Butyl titanate, tetra ethyl titanate and the like can be used.

Zirconium-based coupling agents include pure zirconate tetra normal-propyl zirconate, tetra normal-butyl zirconate, triethanamine zirconate, zirco aluminate carboxy zirco aluminate, and amine group-containing zircon. Aluminate and the like can be used. Others include -OH and -SH groups. These zirconium aluminates are used in polymers such as water-soluble acrylic, alkyd, polyester polymers, epoxy, urethane, etc. It improves the binding force with the components and serves to strengthen the coating film.

The aqueous surface treatment composition of the present invention is generally known as an aqueous composite resin solution in which the organic resins, inorganic components, corrosion-resistant rust-preventing agents and organometallic complexes, and organic solvents, antifoaming agents, smoothing fragrance additives, coupling agents, and the like are soluble in them. It is prepared by dissolving in an aqueous solvent and / or water so that the solid content is 10 to 20% by weight.

If the solid content is less than 10% by weight, the surface-treated composition has a poor ability to continuously apply the entire galvanized steel sheet, and if it exceeds 20% by weight, it is difficult to control the adhesion amount of the surface-treated composition to 1000 mg / m 2 or less, and also the viscosity Is too high for roll coating and spraying.

The surface treatment composition replacing the chromium-containing surface treatment composition according to the present invention is difficult to apply directly to the pretreatment line of the present surface treatment because the surface treatment composition after applying it to a steel sheet is not only very high temperature but also long treatment time. After coating on a silver steel sheet, it can be dried not only at high temperature but also at low temperature of PMT 80-130 degreeC.

The surface treatment composition of this invention is applied so that dry adhesion amount may be 300-1000 mg / m <2> in steel plate. If the dry adhesion amount is less than 300 mg / m 2, corrosion resistance is low, and if it exceeds 1000 mg / m 2, it is difficult to dry.

The surface treatment composition of the present invention not only has excellent corrosion resistance of the steel sheet but also improves the coating performance of baking enamel and the like than the pure chromated steel sheet. In addition, it can be applied to current plating treatment lines as it can be dried at a low temperature of 80 ~ 130 ℃. Furthermore, it is an environmentally friendly and harmless surface treatment composition containing no chromium.

Hereinafter, the present invention will be described in detail through examples.

<Example 1>

As a water-soluble acrylic resin, 200 parts by weight of a mixed resin having an acid value of about 100 and neutralized with tertiary amine and 30:70 parts by weight of an inorganic silica sol, 68 parts by weight of an aqueous solution of hexaammonium hepta molybdate phosphate, triethanol amine zirco 3.9 parts by weight of Nate was dissolved in a solvent mixed with distilled water and methyl alcohol in a 1: 1 weight ratio to prepare a metal surface treatment agent. This was applied to a galvanized steel sheet and dried at 80 ° C. to produce a galvanized steel sheet having an adhesion amount of 0.8 g / m 2.

<Example 2>

300 parts by weight of a resin solution obtained by neutralizing a modified epoxy water-dispersible resin having a hydroxy value of 70 with phosphoric acid and an inorganic silica sol at a solid ratio of 50:50, 88.5 parts by weight of an aqueous solution of molybdenum oxide phosphate, and an organic titanium phosphate complex 6.8 parts by weight of a distilled water and methyl alcohol in a 1: 1 weight ratio of the mixture was mixed so that the solid content 20 parts by weight to prepare a metal surface treatment agent. This was coated on a galvanized steel sheet and dried at 120 ° C. to produce a galvanized steel sheet having an adhesion amount of 0.4 g / m 2.

<Example 3>

As a water-soluble acrylic resin, 200 parts by weight of a resin having an acid value of about 80, a solution neutralized with a tertiary amine, an inorganic silica sol, and a solid content ratio of 60:40 were added, 81 parts by weight of an aqueous solution of molybdenum oxide phosphate and 3.5 parts by weight of phosphoric acid The metal surface treatment agent was prepared by mixing 3.5 parts by weight of diisopropoxy titanium bis ethylaceto acetate in a solution containing 20 parts by weight of solid content in a solvent mixed with distilled water and methyl alcohol in a 1: 1 weight ratio. A galvanized steel sheet having an adhesion amount of 0.9 g / m 2 after coating on a galvanized steel sheet and drying at 90 ° C. was produced.

Comparative Example 1

200 parts by weight of a mixed resin containing an acid value of about 100, a resin solution neutralized with a tertiary amine and an inorganic silica sol in a solid ratio of 20:80, 68 parts by weight of an aqueous solution of hexaammonium hepta molybdate phosphate, and triethanol amine 3.9 parts by weight of zirconate was mixed with a solvent containing distilled water and methyl alcohol in a 1: 1 weight ratio to prepare a metal surface treatment agent. A galvanized steel sheet having an adhesion amount of 0.8 g / m 2 after coating on a galvanized steel sheet and drying at 80 ° C. was produced.

Comparative Example 2

300 parts by weight of a mixed resin having a weight ratio of 50:50 of a solid solution containing a resin solution obtained by neutralizing a modified epoxy water-dispersible resin having a hydroxy value of 70 in phosphate and an inorganic silica sol, 15 parts by weight of an aqueous solution of molybdenum oxide phosphate, and organic titanium 11.8 parts by weight of the phosphate complex compound was mixed in a solvent mixed with distilled water and methyl alcohol in a 1: 1 weight ratio to prepare a metal surface treatment agent. This was coated on a galvanized steel sheet and dried at 120 ° C. to produce a galvanized steel sheet having an adhesion amount of 0.4 g / m 2.

Appearance, adhesion, flat plate corrosion resistance, corrosion resistance of the processed part, workability after top coat, workability of the coating agent, storage stability and powdering property of the galvanized steel sheet treated with the metal surface treatment agent obtained in Examples 1-3 and Comparative Example 1-2 Each evaluation was shown in Table 1 below.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Appearance Adhesion Flat Plate Corrosion Resistance Processing Part Corrosion Resistance After Coating Coating Processability Storage Stability Powder ◎◎◎ O ◎◎ O ◎◎◎ O ◎◎ O ◎◎◎ O ◎◎ O ×× O △ × O × ◎ △△ × △△ O

Evaluation: ◎ Best, Good, Good, Bad

(1) Appearance Evaluation

Visual stains and peelings were observed.

(2) adhesion

After 100/100 cross cut, taping test with cellophane tape.

(3) plate corrosion resistance

5% saline was sprayed at 35 ° C. for 72 hours, and red blue was observed.

(4) Machining part corrosion resistance

After Erichsen was processed to 6mmφ, the specimens were brine and observed the formation of red blue after 48 hours.

(5) Workability after top coat

The coating film after 1000 gr. And 30 cm impact processings of the coating material of home appliances was observed.

(6) storage stability

After storage for 10 days at 30 ℃ change in viscosity (within 10%) was observed.

(7) Powdering property

The degree of powdering phenomenon on the surface was observed after processing with a square cup tester.

From the above results, it can be seen that a film having excellent properties is formed from the surface treatment composition containing no chromium of the present invention.

While the surface treatment composition of the present invention has the ability to prevent corrosion of the steel sheet, the performance of the coating base such as baking enamel is improved more than the pure chromate treated steel sheet. In addition, it is possible to exhibit excellent performance in a low state as PMT 80 ~ 130 ℃ so that the drying temperature can be used in the current plating treatment line. It is a surface treatment agent for water-soluble galvanized steel sheet that does not contain chromium, a heavy metal harmful to humans, and is free from environmental pollution by VOC.

Claims (5)

Surface treatment composition for galvanized steel sheet Based on the weight of solids, 80 to 50% by weight of mixed resins in which water-soluble organic resins and inorganic components are mixed in a solid ratio of 70:30 to 30:70, and phosphate-based corrosion-resistant rust inhibitors of metal oxides 10 to 40% % And organometallic complex 1-20% by weight, As the water-soluble organic resin, a water-soluble or water-dispersible acrylic polymer resin having an hydroxyl group or a carboxyl group and an epoxy resin are used alone or in a mixture of two or more, As the inorganic component, alumina sol, silica sol, titania sol, zirconia sol is used alone or in a mixture of two or more, The phosphate-based corrosion-resistant rust inhibitor of the metal oxide is aluminum, aluminum phosphate, manganese, zinc, molybdenum, phosphate solution of fluorine, phosphate solution of hexaammonium hepta molybdate tetra hydrate and phosphate solution of soda alone or a mixture of two or more Used as The organometallic complex is a surface treatment composition for galvanized steel sheet using a silane coupling agent, a titanium coupling agent and a zirconium coupling agent alone or a mixture of two or more. The surface treatment composition according to claim 1, wherein the surface treatment composition for galvanized steel sheet has a solid content of 10-20% by weight. The surface treatment composition according to claim 1, wherein the drying temperature of the galvanized steel sheet is PMT 80-130 ° C. The surface treatment composition as claimed in claim 1, wherein a phosphate solution is added up to 15% by weight based on the weight of the surface treatment composition solids. The galvanized steel sheet in which the surface treatment composition for galvanized steel sheet of any one of Claims 1-4 was processed by the dry adhesion amount of 300-1000 mg / m <2>.