KR100775311B1 - Multi-functional, high corrosion resistance coating composition for resin coated steel sheet and the resin coated steel sheet - Google Patents

Abstract

A resin composition for a multi-functional and high anti-corrosive steel sheet is provided to ensure low-temperature curing, excellent anti-corrosive property, weldability, adhesion, processability, conductivity and coatability. A resin composition for a multi-functional and high anti-corrosive steel sheet comprises: 10.0-25.0 wt% of an epoxy resin; 5.0-10.0 wt% of an aromatic amine curing agent; 5.0-20.0 wt% of a urethane resin; 5.0-20.0 wt% of calcium ion exchanged amorphous silicon dioxide; 1.0-5.0 wt% of a metal hydrofluoride; and the balanced amount of a solvent. The epoxy resin has a number average molecular weight of 3,000-8,000. The metal hydrofluoride is selected among HPF6, H2TiF6, HZrF6 and H2SiF6.

Description

Multi-Functional, High Corrosion Resistance Coating Composition for Resin Coated Steel Sheet and the Resin Coated Steel Sheet}

1 is a side cross-sectional conceptual view of a resin coated steel sheet.

Figure 2 shows the results of observing the distribution of the metal fluoride acid in the cross section of the coating layer after coating on the surface of the hot-dip galvanized steel sheet using the composition of the present invention, the electron microscope (EPMA; Electron Probe Micro Analyzer) Drawing.

3 is a view showing the result of observing the coating layer cross-section using a scanning electron microscope (SEM) after coating the surface of the alloyed hot-dip galvanized steel sheet using the composition of the present invention (FIG. 2B).

<Description of the symbols for the main parts of the drawings>

1: base steel sheet 2: galvanized layer 3: resin coating layer

The present invention relates to a resin composition for a pre-shielded steel sheet having corrosion resistance and coating film adhesion. More specifically, 10.0 to 25.0 wt% of epichlorohydrin bisphenol A type epoxy resin having a number average molecular weight of 3000 to 8000, and an aromatic amine curing agent 5.0 ~ 10.0 wt%, 5.0-20.0 wt% methylene block diisocyanate urethane resin with 5-10 wt% NCO, 5.0-20.0 wt% calcium ion exchange amorphous silicon dioxide, 1.0-5.0 wt% metal fluoride and residual solvent It is related with the resin composition comprised.

In general, automotive steel sheet manufactured by steel company is subjected to phosphate treatment and painting after assembling the car body in the automobile company. At this time, there are several places where the steel plate overlaps in the assembled body, for example, the hem (Hem) of the door of the car, for example. In this way, since the phosphate treatment solution or paint hardly penetrates the steel plate overlapping part of the vehicle body, the corrosion resistance becomes weak.

In order to solve this problem, the automobile company is used to seal the overlapping parts of the steel sheet (Sealing) to block the corrosion factor access to the site. However, this causes a decrease in productivity and an increase in cost, and thus requires a surface treated steel sheet which can omit the sealing process.

Accordingly, European steel companies produce a steel sheet coated with an organic coating having a thickness of about 2 to 8 μm after galvanizing the steel sheet, treating the chromate or chromium-free pretreatment solution and securing corrosion resistance thereon. This is to ensure corrosion resistance even in the site where the phosphate coating or coating treatment in the automobile company, it is possible to omit the sealing process in the automobile company is called a presealed steel sheet.

However, the surface-treated steel sheet had a problem in that electrical resistance welding (spot welding) deteriorated due to the thick resin film formed to ensure corrosion resistance. In order to solve this problem, a metal powder having excellent electrical conductivity was mixed and used in the resin coating. However, due to the thick resin coating having a thickness of 3 μm or more, the weldability deterioration problem could not be completely solved. In addition, excellent corrosion resistance is required to meet the original purpose of the free shield steel sheet.

In addition, heavy metals such as chromium, lead, mercury, and cadmium are harmful to the human body, and heavy metals in automobiles and home appliances are regulated mainly in the European Union and Japan. Known as a hazardous substance. Therefore, there is a need for an environmentally friendly resin coated steel sheet that does not contain these harmful heavy metals and satisfies the required qualities such as corrosion resistance, weldability, workability, adhesion, and paintability.

Accordingly, the present invention is to solve the problems of the prior art as described above, to be applied to BH (Bake-Hardening) steel sheet, etc., to be cured at a low temperature of less than 160 ℃, while ensuring excellent corrosion resistance, conductive materials such as metal powder An object of the present invention is to provide a resin composition for resin coated steel sheet having excellent weldability, high corrosion resistance, resin adhesion, processability, conductivity, and paintability, and a resin coated steel sheet using the same.

As one aspect of the present invention for achieving the above object,

10.0-25.0 weight% epoxy resin; 5.0-10.0 wt% of an aromatic amine curing agent; Urethane resin 5.0-20.0 wt%; Calcium ion exchange amorphous silicon dioxide 5.0 to 20.0% by weight; 1.0 to 5.0% by weight of metal fluoride; And a resin composition for a multifunctional, highly corrosion-resistant surface-treated steel sheet containing a residual solvent.

In another aspect of the present invention,

Provided is a resin coated steel sheet having a resin coating layer having a dry coating thickness of 1.0 to 3.0 占 퐉 formed by the multifunctional, high corrosion resistant surface treated steel sheet resin composition of the present invention.

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

In the accompanying drawings, Figure 1 is a schematic diagram showing a side cross-section of the resin coated steel sheet corresponding to an embodiment of the present invention. FIG. 2 shows the distribution of the fluorine atoms in the metal fluoride in the cross section of the coating layer after coating the composition of the example prepared from the resin composition of the present invention on the surface of the alloyed hot-dip galvanized steel sheet (EPMA: Electron Probe Micro Analyzer). Figure 3 is a view showing the results, Figure 3 is a view showing the results of observing the coating layer cross-section using a differential scanning microscope (SEM).

In general, the physical properties of the resin coated steel sheet is mainly affected by the resin layer. In particular, the resin in the upper portion of the steel sheet provides a primary shielding effect against the corrosion factor, and also provides a shielding effect to prevent rapid elution or loss of the lower pretreatment layer, and serves to secure corrosion resistance of the resin coated steel sheet. do. If the corrosion resistance of the resin-coated steel sheet is not secured, when applied to home appliances or automobile bodies, hole corrosion of the steel sheet may occur along with corrosion of the body, and the product may be damaged.

In addition, the resin film constituting the upper layer of the pre-shielded steel sheet should provide a function of protecting the lower pretreatment layer, and at the same time, form a solid film having excellent alkali resistance, solvent resistance and chemical resistance. If the resin coating is not strong, the resin coating is not able to withstand the alkaline degreasing solution and the acidic phosphate solution in the degreasing and phosphate treatment process when applied to the product, resulting in the peeling or damage of the resin coated steel sheet. The same physical properties are not achieved.

In addition, the corrosion resistance must be exerted in the hemming area where electrodeposited coating is not applied among the automotive body to which the resin coated steel sheet is applied, and in other parts, the resin is smoothly applied to the electrodeposition coating like the plated steel sheet or cold rolled steel sheet for automobiles. Should be suitable for automotive electrodeposition coating.

In order for the resin film to have an advantageous structure for electrodeposition coating or the like, the resin constituting the resin film preferably contains a hydroxyl group (-OH) or an amine group (-NH ₃ ). Therefore, in the present invention, an epoxy resin is used as the main resin.

The epoxy resin may be an epoxy resin having a number average molecular weight of 3,000 to 8,000, in particular an diglycidyl ether or an epichlorohydrin bisphenol A type epoxy resin. When the number average molecular weight of the epoxy resin is less than 3,000, since the viscosity is low, the coating film is excessively dense and hardened after the reaction with the curing agent, thereby easily causing film removal due to external impact. In addition, when the number average molecular weight is 8,000 or more, the film density decreases and the corrosion resistance becomes weak, and the viscosity of the composition rises, making it difficult to form a uniform coating. It is not preferable to increase manufacturing cost, such as to increase.

The hardening | curing agent for hardening the said epoxy resin is used, A melamine resin is mentioned as a hardening | curing agent used by this invention. In particular, the melamine resin is preferably a methylated melamine resin substituted with a methyl group or a butylated melamine resin substituted with a butyl group.

The melamine resin is preferably added at 5.0 to 10.0% by weight. If the content of the curing agent is less than 5.0% by weight, the curing reaction of the coating film is insufficient to secure the desired physical properties. If the content of the curing agent is more than 10.0% by weight, it is not economical because it does not increase the curing reaction by additional addition, The curing agent is not preferable because it may self-condense and deteriorate solution stability and physical properties of the resin film.

Due to the characteristics of the steel sheet, the chipping resistance is required in order to prevent film removal of the coating film due to external impact. To this end, a urethane resin is added. The urethane resin added in this way is used as a chipping-resistant improvement and the hardening | curing agent of an epoxy resin.

As the urethane resin, it is preferable to use a methylene-based block diisocyanate urethane resin having an NCO content of 5 to 10% by weight and a diblock temperature of 60 to 140 ° C.

Since diisocyanate reacts rapidly with the hydroxyl group of a polyhydric alcohol and an epoxy group at normal temperature, the block diisocyanate which blocked the terminal is used. It is preferable that the urethane resin added has content of 5.0-20.0 weight%. When added in less than 5.0% by weight it is not possible to achieve the desired chipping resistance, when added in excess of 20.0% by weight affects the curing reaction is not desirable because the desired coating film properties do not appear.

In the resin composition of the present invention, metal fluoride acids such as HPF ₆ , H ₂ TiF ₆ , H ₂ ZrF ₆ , and H ₂ SiF ₆ are added to lower the curing temperature. The metal fluoride serves to promote curing by lowering the reaction temperature of the epoxy resin without adversely affecting the bonding strength and weldability of the present resin composition to the underlying metal material or pretreatment layer. In addition, at the same time it is uniformly distributed in the resin layer to play a role of improving the electrical conductivity to ensure excellent weldability.

Reaction formula of the epoxy resin, the block diisocyanate urethane resin, and phosphoric acid used by this invention is as follows.

The metal fluoride acid is preferably contained in the resin composition 1.0 to 5.0% by weight. When the metal fluoride is included in less than 1.0% by weight, it is difficult to lower the curing temperature to 160 ° C or less because it does not cause functional group decomposition of the epoxy resin, and is not effective in improving weldability, and when it contains more than 5.0% by weight. Since the added metal fluoride reacts with the resin itself to cause entanglement or decomposes the resin, it is difficult to achieve desired coating film adhesion, and therefore, it is preferable to have a content in the above range.

In addition, the resin composition of the present invention is added with calcium ion exchange amorphous silicon dioxide to improve the corrosion resistance of the resin coating. It is preferable that the added content is 5.0 to 20.0% by weight, and if the silicon dioxide is less than 5.0% by weight, the effect of improving corrosion resistance is inadequate, and when the content exceeds 20.0% by weight, the silicon component interferes with the conduction to lower the weldability and increases the surface area. Viscosity of the solution due to the large rise and settling easily is not preferable.

The size of the silicon dioxide to be added is preferably an average value of 2.0 ~ 3.6㎛. Silicon dioxide with a size of less than 2.0 μm is undesirable because it is expensive, the solution viscosity is greatly increased due to the increase in the surface area, and the thixotrophy is increased. In addition, when the particle size exceeds 3.6 μm, silicon dioxide is difficult to be uniformly mixed in the resin, and thus, corrosion resistance cannot be expected, and quality problems such as unevenness of the coating surface and lowering of corrosion resistance are not preferable.

In the resin composition of this invention containing each component as mentioned above, a solvent is contained in remainder. The solvent is at least one selected from the group consisting of xylene, methyl ethyl ketone, butyl acetate, butyl cellosolve, cellosolve acetate, diacetone alcohol and the like.

In addition, the resin composition may further include any one or more of the following components.

The composition of the present invention comprises at least one organometallic oxide selected from organic titanate or organic zirconate systems. These organometallic oxides act as catalysts to enhance the binding capacity of calcium ion exchange amorphous silicon dioxide, form chelate compounds to improve corrosion resistance by themselves, and are also attributable to improved weldability due to the inclusion of metal components. The organometallic oxide may be added at 5.0% by weight or less. The addition of more than 5.0% by weight no longer contributes to the improvement of the role of catalyst and corrosion resistance, leading to an increase in cost, and rather to solution gelation.

A dispersant may be added to improve the wettability of the solution and the dispersibility of amorphous silica, and the dispersant may include polyether modified polydimethylsiloxane, hydrofunctional carboxylic acid ester or a mixture thereof. have. The dispersant may be added up to 3.0% by weight. When more than 3.0% by weight is added, the wettability of the solution is excessively increased, making it difficult to control the amount of adhesion during coating.

Furthermore, in order to improve the adhesion to the pretreatment layer and the adhesion to the electrodeposition coating film, ether-based adhesion promoters or phosphate-ester compounds, Al-Zr-based compounds and 3-glycidoxypropyl tree having an water-soluble skeleton having a molecular weight of 150 to 250 One or more adhesion promoters selected from the group consisting of methoxysilanes can be added. The adhesion promoter or adhesion promoter may be added in an amount of 10.0% by weight or less, and when it exceeds 10.0% by weight, the resin may be entangled by reacting with an epoxy resin or the like in the composition. Desired coating properties cannot be obtained such as film removal.

Furthermore, the resin composition of the present invention may optionally add wax to prevent film removal of the resin coating film during molding of the resin coated steel sheet. The wax may include polyethylene (PE), polytetrafluoroethylene (PTFE), carnuba wax, or PE-PTFE mixed or modified wax, and these waxes may be used alone or in combination of one or more. The wax is added in an amount of 3.0% by weight or less based on the resin composition. The addition of 3.0% by weight or more of wax is not effective in reducing the frictional force, and the wax component is eluted to the surface during drying of the coating film to facilitate the penetration of the corrosion factor, which is not preferable because the corrosion resistance is lowered. Furthermore, the wax to be used has a melting point of 100 ° C. or more in terms of workability in providing lubricity after forming a coating film and preparing a solution composition, and it is preferable to use one in which 30 to 40 wt% wax is dissolved in a glycol ether or the like.

The steel plate to which the present invention is applied includes a hot rolled steel sheet, a cold rolled steel sheet, a plated steel sheet, and the like, and is not particularly limited. The plated steel sheet may form a plated layer of zinc, aluminum, or an alloy thereof by electroplating, hot dip plating, vapor deposition, or the like. Hot-dip galvanized steel sheets also include alloyed hot-dip galvanized steel sheets.

Hereinafter, a method of manufacturing a multifunctional, high corrosion resistant resin coated steel sheet using the resin composition will be described in detail.

The steel sheet coated with the resin composition may be a galvanized steel sheet or a zinc alloy plated steel sheet. The galvanized steel sheet or alloyed galvanized steel sheet constitutes a chromium-free pretreatment layer coated with an adhesion amount of 10 to 1,000 mg / m2, or a galvanized steel sheet or galvanized steel sheet which is pretreated with SiOx coating by chemical vapor deposition or physical vapor deposition. Can be.

For the purpose of improving the corrosion resistance of the plated steel sheet can be treated with a chromium-free coating before the resin composition treatment of the present invention. The chromium-free coating is an organic-inorganic compound that does not contain environmentally harmful substances such as chromium, lead, cadmium, and mercury. The chromium-free coating is applied so that the adhesion amount of the dry coating film is 10 ~ 1,000㎎ / ㎡, and then hardened to the steel plate temperature of 40 ~ 120 ℃. After air-cooled or water-cooled. This is because when the thickness of the dry coating film is less than 10 mg / m 2, corrosion resistance and resin adhesion decrease, and when it exceeds 1,000 mg / m 2, the production cost increases without improving corrosion resistance and greatly reduces weldability.

The resin composition according to the present invention is coated on the plated steel sheet, chromium-free or SiOx pretreated plated so as to have a dry coating thickness of 1.0 to 3.0 μm. If the dry coating thickness is less than 1.0 μm, physical properties such as corrosion resistance are lowered. If the dry coating thickness is more than 3.0 μm, the weldability decreases due to the excessive adhesion of the resin.

After apply | coating the resin composition of this invention, it hardens to the steel plate temperature of 120-160 degreeC. If the curing temperature is lower than 120 ℃, the curing reaction of the resin is insufficient, and the physical properties of the coating film are lowered. If the curing temperature is higher than 160 ℃, the curing reaction is further progressed with the change of the material of the steel sheet such as BH (Bake-Hardening) steel sheet. It is not preferable because it consumes only calories without heat.

Hardening of the apply | coated resin composition can also harden by irradiating near-infrared rays, an electron beam, etc.

After the curing, the resin-coated preshielded surface-treated steel sheet is manufactured by cooling using a conventional method such as water cooling or air cooling.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are merely illustrative of one embodiment of the present invention, and do not limit the present invention.

Example

Example  One

In this example, the solution stability of the resin composition and the properties of the resin coating were evaluated according to the resin content and the hardener content.

Melamine resin and urethane resin are blended as the epoxy resin and the curing agent in the amounts shown in Table 1 below, 10.0% by weight calcium ion exchange amorphous silicon dioxide, 3.0% by weight metal fluoride, 2.0% by weight polyether-modified polydimethylsiloxane dispersant, organic 2.0 weight% of titanate and 1.0 weight% of PE wax were mix | blended and the resin composition of Invention Examples 1-6 and Comparative Examples 1-20 was prepared.

Thereafter, solution stability, corrosion resistance, weldability, and adhesion to the solution composition were evaluated.

Solution stability

Solution stability was evaluated as follows according to the presence or absence of gel formation in the solution composition after 30 days at room temperature in consideration of the sufficient time to actually use.

(Double-circle): When a precipitate does not generate | occur | produce and a gel does not form.

(Triangle | delta): When a precipitate generate | occur | produces 5 vol% or less, or a gel partly forms.

X: when precipitate generate | occur | produces 5 vol% or more and a gel is formed

Chromium-free pretreatment was applied to an alloyed hot-dip galvanized steel sheet having a plating deposition amount of 40 to 60 g / m 2 (0.60 to 0.80 mm in thickness) and coated with a dry coating thickness of 500 mg / m 2. After coating so as to be 1.0 ~ 3.0㎛, it was cured at a steel plate temperature of 155 ℃, water cooled and dried to prepare a specimen. Corrosion resistance, weldability and adhesion were evaluated from the prepared specimens.

Corrosion resistance

Corrosion resistance was investigated by using a salt water spray tester (SST) at 35 ° C, and then the corrosion condition was measured by measuring the time until the red blue color occurred more than 5% of the total surface area according to the elapsed time. Same as

◎: Red blue color: Over 1200 hours

○: Red Blue: 1000 ~ 1200 hours

□: Red Blue: 800 ~ 1000 hours

△: Red blue occurrence: 600 ~ 800 hours

×: Red blue occurrence: Within 600 hours

Adhesion

The adhesiveness was collected in a size of 30 mm x 50 mm, immersed in boiling water for 30 minutes, dried, and the degree of peeling was measured using a scotch tape. Evaluation was made according to the degree of resin buried in the tape, the evaluation criteria are as follows.

◎: no peeling on the tape surface

□: Peeling within 5% of area ratio on tape surface

(Triangle | delta): Peeling generate | occur | produces 5% or more with respect to area ratio on a tape surface.

×: Full peeling occurs on the tape surface

Weldability

In order to evaluate the weldability, each specimen was welded using an AC pneumatic spot welder under the conditions of a pressing force of 200 to 300 kgf and an energizing time of 10 to 20 cycles at a welding current of 6 to 8 kA. RWMA Class II of Cu—Cr alloy was used as a welding electrode. Weldability was evaluated by continuous RBI. The specimen for evaluation overlaps two specimens cut to a length of 80 mm and a width of 20 mm to the point of 20 mm from the end, welds one point to the center of the overlapped area, and then examines the number of spots in which the weld is dropped by a tensile tester. It was. This RBI was evaluated as a continuous RBI, and the evaluation criteria are as follows.

◎: 1,200 or more consecutive RBIs

○: Number of consecutive RBIs 1,000 to 1,200

□: Number of consecutive RBIs 800 ~ 1,000

(Triangle | delta): 800 or less consecutive RBIs

×: non-welding

division solution Quality evaluation Epoxy resin Melamine Urethane resin Solution stability Corrosion resistance Adhesion Weldability Molecular Weight content Kinds content Kinds content Comparative Example 1 - 0   Amide resin 20  Block isocyanate 0 △ × × △ Comparative Example 2 1000 20 One 5 △ □ ◎ △ Comparative Example 3 2000 10 5 8 △ ○ ◎ ◎ Comparative Example 4 2000 20 5 10 △ ○ ◎ ◎ Comparative Example 5 5000 15 10 10 △ ◎ □ ◎ Comparative Example 6 10000 20 15 40 × ○ ◎ □ Comparative Example 7 1000 5         Aromatic amine resin One    TDI 0 △ ○ ◎ ○ Comparative Example 8 2000 10 5 2 × □ □ ◎ Comparative Example 9 2000 20 5 8 × △ □ ◎ Comparative Example 10 5000 15 10 20 × □ △ □ Comparative Example 11 10000 20 10 20 × □ △ ◎ Comparative Example 12 10000 15 15 40 × □ × ◎ Inventive Example 1 3000 10 5  Block isocyanate 5 ◎ ◎ ◎ ◎ Inventive Example 2 3000 20 5 8 ◎ ◎ ◎ ◎ Inventive Example 3 5000 15 10 20 ◎ ◎ ◎ ◎ Inventive Example 4 8000 15 10 20 ◎ ◎ ◎ ◎ Comparative Example 13 1000 15 One   MDI 3 △ ◎ □ ○ Comparative Example 14 2000 20 5 10 × ○ □ ○ Comparative Example 15 5000 15 10 25 × ○ □ □ Comparative Example 16 5000 20 10 20 × □ □ ○ Comparative Example 17 10000 5 5 30 × ○ □ ◎ Comparative Example 18 20000 20 One  Block isocyanate 40 △ ○ ◎ □ Inventive Example 5 3000 20 10 10 ◎ ◎ ◎ ◎ Inventive Example 6 5000 15 5 20 ◎ ◎ ◎ ◎ Comparative Example 19 10000 10 5 20 ○ ○ ◎ □ Comparative Example 20 20000 20 10 20 ◎ ○ ◎ □

Example  2

Methylated melamine formaldehyde (manufactured by US Cytec, hereinafter referred to as 'melamine resin') is used as an curing agent in an epoxy resin having a molecular weight of 5,000 based on the epoxy resin, melamine resin, and urethane resin content of Example 1 of Example 1. Types and contents of calcium ion-substituted amorphous silicon dioxide, polysiloxane dispersant, organic Zr oxide, ether-based adhesion promoter having an soluble skeleton, silane compound, PTFE wax, and other solvents were respectively formulated as shown in Table 2, and Comparative Example 21 After preparing the resin compositions of ~ 39 and Inventive Examples 7 to 10 and evaluated the solution stability according to the change of the content of these additives, and the resin compositions of Comparative Examples 21 to 39 and Inventive Examples 7 to 10 After coating on the steel plate by the method, the corrosion resistance, workability, post-process adhesion, resin adhesion and weldability were evaluated.

Machinability

Machinability was evaluated by using an average value of three specimens in an oil-free state by measuring a single-sided friction coefficient by a draw bead method. Evaluation criteria are as follows.

◎: One side friction coefficient is 0.15 or less

□: One side friction coefficient 0.15 or more and 0.18 or less

(Triangle | delta): One side friction coefficient 0.10 or more and 0.20 or less

×: single side friction coefficient 0.20 or more

Adhesion after processing

After processing, the adhesiveness was taken from a circular specimen with a diameter of 95 mm, and a cup was formed to a height of 25 mm. Then, the most severe side surface was evaluated using a scotch tape with a peeling area. Is as follows.

◎: no peeling on the tape surface

□: Peeling within 5% of area ratio on tape surface

(Triangle | delta): Peeling generate | occur | produces 5% or more with respect to area ratio on a tape surface.

×: Full peeling occurs on the tape surface

Solution stability, corrosion resistance, resin adhesion and weldability were evaluated in the same manner as in Example 1.

division additive Property evaluation Amorphous silica Dispersant Organic-Zr ether Silane Wax Solution stability Corrosion resistance Adhesion Machinability Adhesion after processing Weldability Comparative Example 21 5 0 0 0 0 0 △ × × × × ○ Comparative Example 22 5 0.1 0.2 0.5 0.2 0.5 △ ○ □ △ □ ○ Inventive Example 7 5 0.5 0.5 1.0 0.5 2.0 ◎ ◎ ◎ ◎ ◎ ◎ Comparative Example 23 5 One 2.0 5.0 3.0 5.0 ◎ □ ◎ ◎ ◎ ◎ Inventive Example 8 5 2 5.0 3.0 5.0 1.0 ◎ ◎ ◎ ◎ ◎ ◎ Comparative Example 24 5 5 8.0 0.5 8.0 0.5 ◎ ◎ □ △ □ ◎ Comparative Example 25 0 0.1 0.2 1.0 0.2 2.0 ◎ × ◎ ◎ ◎ ◎ Comparative Example 26 5 0.5 0.5 5.0 0.5 5.0 △ □ □ ◎ □ ◎ Comparative Example 27 5 One 2.0 6.0 3.0 0 ◎ ◎ ◎ × ◎ ◎ Comparative Example 28 10 2 5.0 0.5 5.0 0.5 △ ◎ ◎ △ ◎ ◎ Comparative Example 29 10 5 8.0 1.0 8.0 2.0 △ ◎ □ ◎ □ ◎ Comparative Example 30 10 0.1 10.0 5.0 0.2 5.0 △ □ △ ◎ △ ◎ Comparative Example 31 10 0.5 0 6.0 0.5 0 □ ○ ◎ × ◎ ◎ Inventive Example 9 10 One 0.2 0.5 3.0 0.5 ◎ ◎ □ △ □ ◎ Comparative Example 32 10 2 0.5 1.0 5.0 2.0 ◎ ◎ ◎ ◎ ◎ ◎ Comparative Example 33 10 2 2.0 5.0 8.0 5.0 △ ○ ◎ ◎ ◎ ◎ Comparative Example 34 10 0.1 5.0 6.0 0.2 0 △ ◎ ◎ × ◎ ◎ Comparative Example 35 15 0.5 8.0 0.5 0.5 0.5 △ ◎ ◎ △ ◎ ◎ Inventive Example 10 15 One 8.0 1.0 3.0 5.0 △ ○ △ ◎ △ ◎ Comparative Example 36 15 2 5.0 5.0 5.0 2.0 ◎ ◎ ◎ ◎ ◎ ◎ Comparative Example 37 20 5 2.0 6.0 8.0 0 △ ◎ □ × □ □ Comparative Example 38 20 0 0.5 0.5 0.5 0.5 × ◎ □ △ □ □ Comparative Example 39 20 0.5 0.2 1.0 0 2.0 △ ◎ × ◎ × △

Example  3

In this example, the resin compositions of Comparative Examples 40 to 53 and Inventive Examples 11 to 13 were prepared using the solution prepared according to the composition of Inventive Example 7 of Example 2, and the type of acid compound and the amount of fluorinated metal acid. Alternatively, after coating the steel sheet in the same manner as in Example 2, the curing temperature, corrosion resistance, adhesion, and conductivity were evaluated.

conductivity

Conductivity was measured by 10 points on the surface of the steel sheet using a four-probe contact resistance, and the evaluation criteria are as follows.

○: All 10 points have a surface resistance of 1 mΩ or less

(Triangle | delta): 1 mPa or less of surface resistance of 1-9 points, 1 mΩ or more of surface resistance of 1-9 points

X: 10 points or more surface resistance 1 mPa or more

Curing temperature

The curing temperature was evaluated by measuring the highest temperature of the steel sheet with color change of less than 2.0 after rubbing 10 times round-trip by applying MEK to the gauze.

○: cured at the maximum steel sheet temperature of 160

X: hardened at the highest steel sheet temperature of 161 ° C or higher

division Acid compounds Curing temperature Property evaluation Kinds content Adhesion Corrosion resistance conductivity Comparative Example 40  Maleic anhydride 0 × △ △ × Comparative Example 41 One × ○ △ × Comparative Example 42 3 × △ △ × Comparative Example 43 5 × △ △ × Comparative Example 44 10 × △ △ × Comparative Example 45  Acetic acid One × △ × × Comparative Example 46 3 × △ × × Comparative Example 47 5 × × × × Comparative Example 48 10 × × × × Inventive Example 11  Fluoric Acid One ○ ○ ○ ○ Inventive Example 12 3 ○ ○ ○ ○ Inventive Example 13 55 ○ ○ ○ ○ Comparative Example 49 10 ○ △ △ ○ Comparative Example 50  Phosphoric Acid One ○ ○ ○ △ Comparative Example 51 3 ○ ○ ○ △ Comparative Example 52 5 ○ ○ ○ △ Comparative Example 53 10 ○ △ △ △

Example  4

In the present embodiment, the chromium-free pre-treatment so that the dry coating amount is 500 mg / ㎡, the steel sheet thickness is 0.7 mm and the alloyed hot-dip galvanized steel sheet with an adhesion amount of 40 ~ 60 g / m ² of the invention example of Example 2 The resin composition having a composition of 7 was coated with a dry film thickness of Table 4 at a steel sheet temperature of 160 ° C., and then evaluated for corrosion resistance, resin adhesion, adhesion after welding, and weldability using comparative materials and inventive materials.

division Manufacture conditions Quality evaluation Coating thickness (μm) Corrosion resistance Adhesion Adhesion after processing Weldability Comparative material 0.5 × △ △ ◎ Comparative material 0.8 × ◎ △ ◎ Invention 1.0 ○ ◎ ◎ ◎ Invention 2.0 ◎ ◎ ◎ ◎ Invention 3.0 ◎ ◎ ◎ ◎ Comparative material 3.5 ◎ ◎ ◎ □ Comparative material 4.0 ◎ □ △ △ Comparative material 4.5 ◎ □ □ ×

The resin composition of the present invention is used in the manufacture of a resin layer of a thin film type resin coated steel sheet which can be cured at low temperature, and a drop in curing temperature by metal fluoride and conductivity, ensuring weldability, corrosion resistance by resin components and rust inhibitors, and chipping resistance by urethane resin. , Silane, resin adhesion improvement by ether compounds, solution stability by dispersant, corrosion resistance by organic Ti component, improvement of weldability, ease of coating work by dispersant, ease of processing by wax and the like.

The resin coating for resin coated steel coated on the solution composition and processing conditions of the present invention, such as cold rolled steel, galvanized steel or zinc alloy plated steel exhibits excellent corrosion resistance, conductivity, weldability, chipping resistance, adhesion, solution stability, and workability. Resin layer fabrication of pre-shielded steel plate used in the rear part of automobiles or in areas where phosphate coating or electrodeposition coating film is difficult to form, such as heme, high corrosion resistance organic coating steel sheet for automobile interior and exterior, electrical conduction It is used suitably for manufacture of the resin layer of a steel plate.

Claims (17)

10.0-25.0 weight% epoxy resin; 5.0-10.0 wt% of an aromatic amine curing agent; Urethane resin 5.0-20.0 wt%; Calcium ion exchange amorphous silicon dioxide 5.0 to 20.0% by weight; 1.0 to 5.0% by weight of metal fluoride; And Residual solvent; Multifunctional, high corrosion-resistant surface-treated resin composition comprising a. The method of claim 1, The epoxy resin is a resin composition for multifunctional, highly corrosion-resistant surface-treated steel sheet, characterized in that the number average molecular weight is 3,000-8,000. The method of claim 2, The epoxy resin is diglycidyl ether bisphenol A type epoxy resin, epichlorohydrin bisphenol A type epoxy resin, or a mixture thereof. The method of claim 1, The aromatic amine curing agent is a resin composition for multifunctional, high corrosion resistance surface treatment steel sheet, characterized in that the melamine resin. The method of claim 4, wherein The melamine resin is a resin composition for a multifunctional, highly corrosion-resistant surface-treated steel sheet, characterized in that the terminal is a methylated melamine resin substituted with a methyl group or a butylated melamine resin substituted with a butyl group. The method of claim 1, The urethane resin is a multifunctional, highly corrosion-resistant surface-treated steel sheet resin composition, characterized in that the NCO content of 5-10% by weight, diblock temperature is 60-140 ℃ methylene block diisocyanate urethane resin. The method of claim 1, The metal fluoride acid resin composition for a multi-functional, highly corrosion-resistant surface-treated steel sheet, characterized in that at least one selected from the group consisting of HPF ₆ , H ₂ TiF ₆ , HZrF ₆ and H ₂ SiF ₆ . The method of claim 1, The calcium ion exchange amorphous silicon dioxide is a resin composition for a multifunctional, highly corrosion-resistant surface-treated steel sheet, characterized in that the average particle diameter is 2.0-3.6㎛. The method of claim 1, Resin composition for a multifunctional, highly corrosion-resistant surface-treated steel sheet further comprises an organic metal oxide content of 5% by weight or less. The method of claim 9, The organometallic oxide is an organic titanate, an organic zirconate or a mixture of these, characterized in that the resin composition for a high corrosion-resistant surface-treated steel sheet. The method of claim 1, A resin composition for a multifunctional, highly corrosion-resistant surface-treated steel sheet, further comprising a dispersing agent which is a polyether-modified polydimethylsiloxane, a hydrofunctional carboxylic acid ester, or a mixture thereof at 3.0 wt% or less. The method of claim 1, 10 wt% or less of at least one selected from the group consisting of an ether adhesion promoter, a phosphoric acid ester compound, an Al-Zr compound, and 3-glycidoxypropyltrimethoxysilane having an aqueous skeleton having an molecular weight of 150 to 250 Resin composition for multifunctional, high corrosion resistance surface treatment steel sheet further comprising. The method of claim 1, 10.0 wt% or less further comprising at least one wax selected from the group consisting of polyethylene (PE), polytetrafluoroethylene (PTFE), carnuba wax, PE-PTFE mixed wax, or modified wax thereof A resin composition for multifunctional, highly corrosion-resistant surface-treated steel sheet. The method of claim 1, A resin composition for a multifunctional, highly corrosion-resistant surface-treated steel sheet further comprising at least one curing accelerator selected from the group consisting of p-toluenesulfonic acid, dibutyltin dilaurate and an organic / inorganic acid catalyst at 2.0 wt% or less. The method of claim 1, Wherein said solvent is at least one selected from the group consisting of xylene, methyl ethyl ketone, butyl acetate, butyl cellosolve, cellosolve acetate and diacetone alcohol. A resin coated steel sheet having a resin coating layer having a dry film thickness of 1.0 to 3.0 µm formed by the resin composition of any one of claims 1 to 14. Steel plate; A chromium-free pretreatment layer having an adhesion amount of 10 to 1,000 mg / m 2 or a SiO x layer formed by chemical vapor deposition or physical vapor deposition having a thickness of 10 to 500 nm; And A resin film layer having a dry film thickness of 1.0 to 3.0 µm formed by the resin composition of any one of claims 1 to 14; Resin coated steel sheet comprising a.

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