KR100264982B1 - Preparation of epocy resin composition having good electrodepositing property and good welding property, and zinc coated steel plate by using thereof - Google Patents

Abstract

PURPOSE: A method for preparing an aqueous epoxy resin composition is provided for having good electrostatic painting ability and welding property by comprising metal salt specially treated and the process for producing resin coated galvanized steel sheet by using the epoxy resin composition. CONSTITUTION: The method for preparing an aqueous epoxy resin composition comprises the first step of preparing epoxy resin solution by adding amide resin as the hardening agent to the epoxy resin having number mean molecular weight of 500-4,000 according to the equation of (amount of the hardening agent added(phr)=equivalent value of amine/equivalent value of epoxy x 100); the second step of mixing NiSO4, ZnSO4, CuSO4 and MgSO4 alone or in combination with at least two of them and dissolving it in water to be 5-50 phr to form insoluble metal salt, and then adding 7.5-40phr of liquid ammonia to form sludge of the insoluble metal salt and remove the sludge to result in metal solution containing the stable complex; the third step of adding 3-20 wt.% (in solid content) of the metal solution.

Description

Manufacturing method of water-soluble epoxy resin solution composition excellent in electrodeposition coating property and weldability and manufacturing method of resin coated electro galvanized steel sheet using epoxy resin solution composition

1 is a graph showing the change of each ion and sludge content in the aqueous nickel sulfate solution with respect to the amount of ammonia water added,

2 is a graph showing the relationship between the metal ion content and the weldability reacted with ammonium ions.

The present invention relates to a method for preparing a water-soluble epoxy resin solution composition having excellent electrodeposition coating property and weldability, and a method for manufacturing a resin coated plating steel sheet using the prepared epoxy resin solution composition, and more particularly, to a water-soluble epoxy resin solution to which a treated metal salt is added. It relates to a composition and a method for producing a resin coated steel sheet using the same.

In accordance with anti-rust reinforcement regulations, demand for highly corrosion-resistant surface-treated steel sheets (hereinafter referred to as organic-coated steel sheets) of chromate and resin treatment on zinc nickel electroplated steel sheets is increasing rapidly. The properties of the organic coated steel sheet are largely influenced by the chromate and the resin layer. In particular, the resin in the upper portion of the steel sheet exhibits a primary shielding effect against corrosion factors, and also prevents the rapid chromium elution of the lower chromate layer. Corrosion resistance is improved. However, the corrosion resistance is increased by coating and protecting the lower chromate layer by the resin film of the thin film constituting the upper layer, but the weldability and electrodeposition coating property are lowered than the zinc nickel steel sheet due to the electrical resistance of the resin itself.

In this connection, conventionally, the conductive metal powder was added to the resin solution to improve the weldability. However, when the metal powder is added to the water-soluble resin, the metal powder is difficult to be dispersed in the water due to the high surface tension of the water. The appearance is damaged.

Accordingly, an object of the present invention is to provide a water-soluble epoxy resin solution composition for steel sheet treatment, and a method for manufacturing a resin coated plated steel sheet using the same, by which metal ions are uniformly dispersed in the resin solution, thereby improving weldability and electrodeposition coating property.

According to one aspect of the invention,

(1) preparing an epoxy resin solution by adding an amide resin to the epoxy resin having a number average molecular weight of 500-4000 as a curing agent in an amount calculated by the following formula (1);

Curing agent addition amount (phr) = amine equivalent / epoxy equivalent × 100... (One)

(2) Nickel sulphate (NiSO ₄ ), zinc sulphate (ZnSO ₄ ), copper sulphate (CuSO ₄ ) and magnesium sulphate (MgSO ₄ ) alone or in combination of two or more of them, dissolved in water to give 5-50 phr, and the metal solution is dissolved. Manufacturing step; Preparing a metal complex in which a stable complex is formed by adding sludge to undissolved metal salt by adding 7.5-40 phr of ammonia water to the metal solution and then removing the sludge;

(3) adding a metal solution having the stable complex to the epoxy resin solution at 3-20% by weight relative to the resin solid content; Method for producing a water-soluble epoxy resin solution composition for coating the steel sheet having excellent electrodeposition coating properties and weldability; This is provided.

Further, in another aspect of the present invention, after the epoxy resin coating treatment composition is applied to the chromate-treated electrogalvanized steel sheet so that the dry resin film thickness is 0.5-3.0 μm, the resin is baked at a steel plate temperature of 140-200 ° C. Provided is a method for manufacturing a coated plated steel sheet.

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

In order to improve the electrodeposition coating property and weldability by coating the resin solution composition on the steel sheet, the physical properties of the resin should be controlled. First, in order to increase the electrodeposition coating property, the resin should not be degraded by alkali (pH 10) generated at the interface between the resin film and the electrodeposition paint during electrodeposition coating, and water or other ion exchanges should be easy. In addition, weldability is a method of impregnating a conductive material in the coating by adding a conductive material to the resin solution, but in the case of a water-soluble resin, the conductive material is difficult to disperse and the resin is thinly applied, which is a significant restriction when adding the conductive material. Therefore, the conductive material to be added should be dissolved in water in the solution state and exist in the ionic form. Therefore, in the present invention, an epoxy resin having excellent electrodeposition coating properties is used as a theme, and ammonia is added to the metal solution instead of the conductive metal powder to remove unreacted metal salts by sludge removal, and dissolved metal ions and sulfate groups react with ammonium groups. By adding a metal solution in which a stabilized metal complex is formed to an aqueous epoxy resin solution, metal ions are easily dispersed in the resin solution and thus are uniformly present during film formation, thereby improving electrodeposition coating property and weldability of the coating.

As the water-soluble epoxy resin used as the main solution in the present invention, an epoxy resin having a number average molecular weight of 500-4000 and an amide resin as a curing agent are used. The said epoxy resin is excellent in electrodeposition coating property compared with other resin. On the other hand, if the number average molecular weight of the epoxy resin is 500 or less, crosslinking reaction becomes difficult by low temperature heat drying, and if it is 4000 or more, it is difficult to disperse in water and it is difficult to manufacture a water-soluble resin.

The amount of the curing agent added is calculated by the following formula (1).

Curing agent addition amount (phr) = amine equivalent / epoxy equivalent × 100... (One)

On the other hand, the metal ion solution added to the water-soluble epoxy resin solution is prepared as follows.

First, sulfate metal compounds such as nickel sulfate (NiSO ₄ ), sulfuric acid salt (ZnSO ₄ ), copper sulfate (CuSO ₄ ), and magnesium sulfate (MgSO ₄ ) may be added alone or mixed to water to add 5-50 phr (per 100 parts by weight of solvent). After dissolving to the amount of solute (per hundred), excess ammonia water is added thereto. After adding ammonia water, sludge is formed over time, and the sludge is filtered off. The ammonia water is added in an amount of 7.5-40 phr to the aqueous metal salt solution. If the amount of ammonia water added is less than 7.5 phr, the content of the desired metal ion is less than before the input, and if it is 40 phr or more, it is preferable to add ammonia water at 7.5-40 phr because the content of the metal ion is not increased.

The total amount of sludge generated when the ammonia water is added is less than the concentration of the metal salt initially introduced. When the metal salt is dissolved in water, it coexists in equilibrium in solution in the form of metal salt (MeSO ₄ ), metal cation (Me ⁺ ) and sulfate anion (SO ₄ ^2- ). The dissolved metal cations and sulfate anions are present in a stable complex state in the solution by reacting with ammonia, but the undissolved metal salts react with ammonia to form sludge.

The reaction mechanism is described with reference to FIG. 1 as follows.

1 is a graph showing the amount of sludge and the change of Ni ²⁺ and SO ₄ ^2- contents in the upper layer depending on the amount of ammonia water added, which is applicable to other sulfate metal compounds.

From FIG. 1, it can be seen that the metal cation content is greatly changed based on the added amount of 5 phr ammonia water. In particular, it can be seen that the metal cation concentration is increased at 7.5 phr or more compared to before adding ammonia water.

In addition, as a result of measuring the amount of sludge generated by the addition of ammonia water, it was found to be inversely proportional to the concentration of metal cations. The amount of sludge increased and decreased from 7.5 phr of ammonia water. Sulfate anion (SO ₄ ^2- ) also decreases as the amount of ammonia added increases, which can be explained as follows. In other words, in the aqueous solution, the sulfate metal compounds exist in the form of Me ⁺ , SO ₄ ^2- , and MeSO ₄ in equilibrium with forward and reverse reactions. As soon as ammonia water is added, ammonium, Me ⁺ , ammonium, SO ₄ ^2- and The ammonium group and MeSO ₄ react respectively. Me ⁺ and SO ₄ ^2- react with ammonium ions, respectively, to form stable complexes of the form [Me (H ₂ O) ₂ (NH ₃ ) ₄ ] and (NH ₄ ) ₂ SO _4, which are present in the upper layer of the solution. Undissolved MeSO ₄ reacts with ammonium ions to form sludge and is present in the lower layer. Adding more ammonia water (7.5 phr) leads to a more positive reaction, resulting in more Me ⁺ and SO ₄ ^2- than NiSO ₄ in the required solution, which increases the amount of stabilized metal complex and ammonium sulfate in the aqueous solution. Sludge is reduced. That is, the content of a relatively stable metal complex is increased by sludgeizing and removing the sulfate metal salt that inhibits current conduction by adding ammonia water.

Hereinafter, a method of manufacturing a resin-coated electrogalvanized steel sheet using the water-soluble epoxy resin solution composition of the present invention will be described in detail. The water-soluble epoxy resin solution composition of the present invention is preferably applied to an electrogalvanized steel sheet in consideration of the workability and weldability of the steel plate after coating plating amount and resin coating.

It is prepared by a reactive or coated chromate treatment on an electrogalvanized steel sheet by a conventional method and applying the water-soluble epoxy resin solution composition of the present invention thereon.

The chromate solution of the lower layer used at this time is a coating type chromate treatment agent advantageous in terms of improving corrosion resistance. The coated chromate solution is a conventional solution in which chromic anhydride is dissolved in water and phosphoric acid, silica, silane, and the like are added, but due to the stability of the chromate solution, it is preferable to use the two-component form of chromium solution and silane. In addition, the amount of chromium on the steel sheet during the chromate treatment is 30-200mg / m ² level is less than 30mg / m ² If the corrosion resistance is not enough, the coating film adhesion and workability is deteriorated when 200mg / m ² or more.

And the most important factor in the production of resin steel sheet is the resin coating film adhesion amount is preferably applied so that the thickness of the dry resin coating film is 0.5-3.0μm. When the dry coating thickness is 0.5 μm or less, the coating film is thin, and thus it is difficult to expect sufficient corrosion resistance. When the dry coating thickness is 3.0 μm or more, part of the coating film is peeled off during processing, thereby not exhibiting sufficient corrosion resistance effect. On the other hand, it is preferable to bake the applied resin film at 140-200 ° C after applying the epoxy resin solution composition. If the baking temperature is less than 140 ℃, the resin hardening reaction is insufficient and the physical properties of the coating film are lowered. Above 200 ℃, the material properties of the base steel are not changed and the properties of the BH (baking hardening) steel sheet cannot be preserved. to be.

Hereinafter, embodiments of the present invention will be described in detail.

Example 1

Resin solution Comparative Material 1-5 and Inventive Material 1 were prepared by using the resins shown in Table 1 as the main agent and the curing agent in the amounts described, and dissolving them in water at 10 phr.

Specimen specimen having a thickness of 0.7mm, a coating weight 30g / m ² Cr coating weight is 50mg / m ² of a chromate treatment of zinc alloy electroplated material 1-5 and Comparative material 1, resin solutions invention the dry film thickness of the steel sheet to 1.0 The coating was carried out using a bar coat to be μm, followed by baking at 150 ° C. steel sheet temperature, followed by water cooling to prepare a resin coated steel sheet. Electrodeposition coating property of this resin steel sheet was evaluated and the results are shown in Table 1 below.

At this time, electrodeposition coating conditions were simulated by car treatment process, and degreasing (Chemical name: Pyroclean 442, Concentration: 5% by weight, Treatment time: 3 minutes, Temperature: 50 ° C) and Phosphate treatment (Chemical name: Bonderite 699D, Temperature: 45 ° C, Acidity) : 20.5, free acidity 1.05, acceleration: 2.5), the electrodeposition coating properties (chemical name: ED-1800 Gray, solid content: 20%, temperature: 28 ℃, treatment time: 180 seconds, voltage: 220V) was evaluated.

TABLE 1

The curing agents and the subjects used in the above examples are as follows.

Epoxy-acrylic resin: KDW-814W15 by Kukdo Chemical with pH 9.0, specific gravity 1.0 g / m ³ , viscosity 15 cps

Ester-urethane resin: Neonez R-961 from Zenca

Ethylene acrylic resin: NNCK-K100 of Aekyung Industrial Co., Ltd.

Acrylic urethane resin: Neonez R-940 from Zenca

Epoxy Resin: KD Chemical's YD-017 with water content of 4,000 bisphenol A type with water average molecular weight of 50%

Melamine: Cymel 325 from Cytec

Isocyanate: Aekyung Chemical's BN-69 with 7% regenerated NCO, nonionic and emulsified in water with 40% solids

Imide resin: H-4120 of Kukdo Chemical

Amide resin: Kukdo Chemical's H-4121 with amine value of 170-220 and solid content of 80%

As shown in Table 1, when the epoxy resin and the amide resin were used as the curing agents, the electrodeposition coating properties were superior to those of the other resins. This is because the resin coating is not deteriorated in the alkaline atmosphere generated at the interface between the steel sheet and the electrodeposition paint during electrodeposition coating, and ion exchange of water and various paints is performed.

Example 2

Amide resin (H-4121 from Kukdo Chemical Co., Ltd.) was added to 4.6 phr based on Formula (1) to a water-soluble epoxy resin (YD-017 from Kukdo Chemical Co., Ltd.) diluted to 15% solids with a number average molecular weight of 4,000. Dissolved at 10 phr.

Aqueous ammonia water was then added in an aqueous solution of nickel phosphate in the amounts shown in Table 2, respectively, and then a stabilized metal solution from which sludge was formed was added to the water-soluble epoxy resin solution at 1, 3, 5, 10, 20, and 25 phr, respectively.

Specimens were prepared in the same manner as in Example 1 and evaluated for weldability. The results of solution stability and weldability according to the solution composition and the continuous score after spot welding for each metal salt type are shown in Tables 2 and 2, respectively. .

Weldability was evaluated for spot weldability. At this time, the welding machine was subjected to a tensile test at 200 RB intervals by stopping the air compression welding machine (DAIHEN RPA-33A) at a pressure of 250 kgf and 20 cycles for 20 cycles with 15 cycles of welding time. Was set as the number of continuous RBIs by the number of welds above the standard.

TABLE 2

By adding ammonia water from Table 2 and FIG. 2, the energizing disturbance material is sludged and removed, and the metal ions are present in a stable metal complex salt form, so that the metal salt is uniformly dispersed in the resin solution composition. Therefore, energization is facilitated and weldability is also improved. Furthermore, it can be seen that when the stabilized metal solution is added to the resin solution within the scope of the present invention, solution stability is shown.

Example 3

Inventive material of Example 2 (when the amount of ammonia water and the amount of the metal solution in the resin solution were 20 phr, respectively) was applied to the chromate-treated electrozinc alloy plated steel sheet having a chromium deposition amount of 50 mg / m ² , respectively. The coating was evaluated for corrosion resistance, and the results are shown in Table 3 below.

When the corrosion resistance is light, the processed material is coated with lubricant and processed using a molding tester under the conditions of punch diameter 50mmФ, die diameter 52mmФ, bias and die R 5mm, height 25mm, and then degreasing by simulating the automobile body treatment process together with the plate material. (Chemical name: Pyroclean 442, Concentration: 5% by weight, Treatment time: 3 minutes, Temperature: 50 ° C) and Phosphate treatment (Pharmaceutical name: Bonderite 699D, Temperature: 45 ° C, Acidity: 0.5, Free acidity: 1.05, Acceleration: 2.5) After 6 hours of salt spraying using a composite corrosion tester and dried for 4 hours at 60 ℃ and 14 hours wet phase (95% RH) at 50 ℃ 1 cycle (total 24 hours, including the temperature transition time) Relative comparison of each specimen's condition over time was evaluated.

TABLE 3

As shown in Table 3, when the thickness of the resin coating film is 0.5 μm or less, the coating amount is not uniform, and the corrosion resistance is lowered. When the thickness of the resin coating film is 3.0 μm or more, the resin coating is peeled off and the corrosion resistance is degraded.

By using epoxy amide resin as described above, the electrodeposition coating property is improved, and by adding a metal salt solution stabilized by ammonium ion into the water-soluble epoxy amide resin solution, an electro-alloy galvanized steel sheet having improved weldability and electrodeposition paintability can be manufactured. have.

Claims (2)

(1) preparing an epoxy resin solution by adding an amide resin to the epoxy resin having a number average molecular weight of 500-4000 as a curing agent in an amount calculated by the following formula (1); Curing agent addition amount (phr) = amine equivalent / epoxy equivalent × 100... (One) (2) Nickel sulphate (NiSO ₄ ), zinc sulphate (ZnSO ₄ ), copper sulphate (CuSO ₄ ) and magnesium sulphate (MgSO ₄ ) alone or in combination of two or more of them, dissolved in water to give 5-50 phr, and the metal solution is dissolved. Manufacturing step; Preparing a metal complex in which a stable complex is formed by adding sludge to undissolved metal salt by adding 7.5-40 phr of ammonia water to the metal solution and then removing the sludge; (3) adding a metal solution having the stable complex to the epoxy resin solution at 3-20% by weight relative to the resin solid content; Method for producing a water-soluble epoxy resin solution composition for coating the steel sheet having excellent electrodeposition coating properties and weldability. A method for producing a resin-coated galvanized steel sheet according to claim 1, wherein the water-soluble epoxy resin solution composition is coated on a chromate-treated galvanized steel sheet so as to have a dry resin film thickness of 0.5 to 3.0 μm, followed by quenching at a steel sheet temperature of 140 to 200 ° C.