KR100368215B1 - Resin solution and a method of manufacturing steel sheets by using it - Google Patents

Abstract

PURPOSE: Provided are a resin solution having excellent workability, solution stability, and darkening property after processing, and a method for producing a resin-coated steel plate by using the same. CONSTITUTION: The resin solution which is coated on a chromate-passivated and electrogalvanized steel plate, is characterized by comprising an ethylene-acryl resin solution obtained by mixing an ethylene-acryl resin, 10-20 phr of silica, and 0.1-3 phr of silane coupling agent; and 3-5 phr of epoxy resin having molecular weight of more than 900 less than 1500. The method for producing a resin-coated steel plate comprises applying the resin solution on the desired steel plate so as to have a thickness of dried coating of 0.5-3.0 micrometers, and then baking the applied steel plate at 80-180 deg.C.

Description

Resin solution and a method of manufacturing steel sheets by using it with excellent workability, solution stability and blackening after processing

The present invention relates to a resin solution applied to a chromate-treated galvanized steel sheet and a method for producing a resin coated steel sheet using the same.

Electro-galvanized steel sheet is widely used for home appliances and automobiles because of the uniform coating adhesion, adhesion between the base iron and the plating layer and excellent surface appearance. By the way, when the galvanized steel sheet is put into the demand processing process, the surface is easily contaminated with organic substances or fingerprints of workers in the workplace, and the contaminated parts have quality problems that affect the corrosion resistance and paintability. . Therefore, an anti-fingerprint steel sheet is formed and commercially available on the electro-galvanized steel sheet and subjected to resin treatment after the chromate coating treatment of the thin film.

However, there are various problems in the production of such anti-fingerprint steel sheet. First, as a workability, a conventional resin solution for a steel plate (hereinafter, simply referred to as a 'resin solution') is a pick-up roll 1 as a coater pan 2. ) Is transferred to the applicator roll (4) through a transfer roll (3) and applied to the steel sheet (5). At this time, when the solution transferred from the pickup roll 1 is transferred to the transfer roll 3 and the upper catroroll 4 and the adhesive resin is picked up on the roll and dried, the adhesive resin picked up on the roll as shown in FIG. 2. In (6), the resin solution is not uniformly coated on the surface of the steel sheet, which has caused surface defects of the steel sheet and uneven resin adhesion amounts and defects of resin streaks. In addition, when the roll is wiped with a solvent or a loofah to remove the pick-up component on the roll, the surface of the roll is damaged and the surface of the resin coated steel sheet is poor.

Next is the solution stability, and the current resin solution has a short solution storage period, so the remaining resin solution used in the current month should be disposed of. This is because if the resin is carried forward without disposal, the resin solution will gel over time and cannot be carried over.

Next, in the case of the torn steel sheet worked in the field after blackening after processing, it is manufactured as a finished product through various processes such as cutting, punching, processing, etc. according to the needs of customers. During this process, blackening phenomenon of blackening of processing surface occurs due to damage of resin coating film and plating surface by crushing die surface and steel plate in press machine. There is a problem that often causes complaints.

Therefore, in the related art, quality problems such as pick-up property, solution storage property, and blackening after processing of the steel sheet have arisen in the prior art, so that a credit solution is required to improve it.

SUMMARY OF THE INVENTION An object of the present invention is to provide a resin solution in which adhesive pickup property is prevented, water washing property is improved, workability is excellent, solution stability is secured, and work blackening is prevented after being coated on a steel sheet.

Further, another object of the present invention is to provide a method for producing a resin coated steel sheet excellent in the surface coating properties and coating adhesion properties of the steel sheet using the resin solution.

1 is a schematic diagram of a facility for coating a resin on a steel sheet using a coating roll;

2 is a schematic view showing an aspect in which an adhesive resin component is picked up on each roll;

3 is a graph showing corrosion resistance according to resin adhesion amounts.

Explanation of symbols on the main parts of the drawings

1 .... pickup roll 4 ....

2 .... coater pan 5 .... steel plate

3 .... Transfer roll 6 .... Adhesive resin

The first resin solution of the present invention for achieving the above object is composed of an epoxy resin: 3-5phr containing a molecular weight of 900 or more to less than 1500 to the silica-modified ethylene-acrylic resin solution.

In addition, the second resin solution of the present invention is composed of an epoxy resin having a molecular weight of 900 or more and less than -1500: 3-5 phr and 2-20 fluorine or fluorine-ethylene wax with respect to the silica-modified ethylene-acrylic resin solution.

In the resin coated steel sheet of the present invention for achieving the above another object, in the method of manufacturing a resin coated plated steel sheet to form a resin coated layer thereon, using a chromate-treated electrogalvanized steel sheet as a base steel sheet, the above on the base steel sheet It is composed by applying the first resin solution or the second resin solution so that the dry film thickness is 0.5-3.0 μm, and then baking the coated steel plate at 80-180 ° C.

Hereinafter, the present invention will be described in detail.

First, the phenomenon of roll pickup and a solution thereof will be described.

As mentioned above, the resin solution is coated with a resin in a coater pan on a pickup roll, transferred to a transfer roll, and finally applied to a steel sheet by an applicator, and then dried in an oven to form a resin film. have. At this time, the resin adhesion amount to be attached is adjusted by the driving direction of each roll, the rotational speed, the adhesion pressure between the rolls, and the like. In this case, the resin solution is subjected to chromate treatment on an electrogalvanized steel sheet, and then a resin solution prepared by using a epoxy resin as a curing agent on a main solution of silica-modified ethylene-acrylic resin is applied to a steel sheet by a roll coating method. We carry out.

The present inventors have analyzed the cause of stickiness on the roll when the resin solution is coated under the above conditions, and it can be seen that the degree of occurrence of the adhesive resin pick-up is different depending on the type of curing agent used in the resin solution. In other words, the lower the molecular weight, the more sticky material is attached to the roll during the operation, which causes various quality problems such as streaks in the resin coating. This resulted in poor washability. This adhesive resin pick-up aspect is as shown in FIG. The epoxy resin which functions as a conventional hardening | curing agent uses the thing with little molecular weight. Therefore, due to the resin manufacturing characteristics, it can only be prepared in the liquid phase, and it is dispersed in water and added to the main solution as a curing agent, and this resin solution is a sticky adhesive material that is an epoxy resin component after evaporation of water on the roll during the fingerprinting work. The accumulation on the roll is causing various problems.

To solve this problem, when epoxy resin with high molecular weight is dispersed in water and used as a curing agent, it is present in the solid phase when temporarily evaporating water on the roll and then wet again with the resin solution which is continuously supplied with subsequent roll rotation. The phenomenon which accumulates on a roll will disappear.

Next, as described in terms of securing the stability (storability) of the solution is as follows.

In the present invention, a method for improving the storage performance of a solution is used simultaneously. First, conventionally, a low molecular weight epoxy resin was used as a curing agent. A low molecular weight epoxy resin has much more sites that can react per unit weight than a high molecular weight epoxy resin, and thus, silica-modified ethylene-acryl Promote reactivity with the resin. Therefore, in order to improve solution stability, it is possible to solve the problem by using a high molecular weight epoxy resin as in the above pickup improvement.

Second, there is an advantage in that the solution stability can be greatly improved by chemically bonding with ethylene-acrylic resin as a silane coupling agent in the prior art physically introduced into the solution to improve the corrosion resistance in the solution.

Next, blackening after processing can be improved by adding wax in the resin solution. In the case of ethylene or propylene wax, there is no significant effect on the improvement of blackening after processing.However, when fluorine or fluorine-ethylene wax is added to the resin solution, it gives the slip and lubricity of the dried coating film after application of the solution. It has a significant effect on improving Mars.

The above-mentioned first and second resin solutions of the present invention which can improve the roll pickup prevention and solution stability and blackening properties after processing will be described in detail.

The silica-modified ethylene-acrylic resin solution of the present invention may be formed by chemically combining ethylene-acrylic resin and silica. Specifically, silica is added in an amount of 10-20 phr (pehundred; 100 parts by weight of solvent) to ethylene-acrylic resin. Content) and 0.1-3 phr of silane coupling agent. At this time, when the silica content is less than 10 phr, the corrosion resistance of the resin is deteriorated. When the silica content is more than 25 phr, the silica does not adhere to the resin any more, so that it is difficult to secure desired physical properties such as solution stability (storability). In addition, when the silane coupling agent is less than 0.1 phr insufficient amount of bonding silica and resin to each other, if more than 3 phr is not effective due to the excessive input. In addition, the silane coupling agent may include gamma-glycioxyoxytriethoxysilane.

The ethylene-acrylic resin, silica and silane coupling agent prepared as described above need to be stirred at an appropriate temperature to make a silica-modified ethylene-acrylic resin solution. At this time, the temperature and the stirring time vary depending on the silane coupling agent, which makes it difficult to limit. However, when gamma-glycioxy propyltrimethoxysilane is used as the silane coupling agent, it is necessary to stir at a temperature of 40-95 ° C. for 3-6 hours. The reason is that when the temperature is less than 40 ℃ does not occur denaturation, when the temperature exceeds 95 ℃ the solution does not boil properly degeneration occurs.

When the obtained silica-modified ethylene-acrylic resin solution contains an epoxy resin having a high molecular weight, a first resin solution having excellent workability and securing solution stability is obtained. At this time, the molecular weight of the epoxy resin is 900-1500, the content is preferably 3-5phr for the silica-modified ethylene-acrylic resin solution. The reason is that if the molecular weight of the epoxy resin is less than 900, the adhesive pick-up material increases on the roll, and the quality and roll cleaning performance deteriorate. In addition, when the content of the epoxy resin is less than 3phr hardening reaction is not made sufficiently to secure the chemical resistance, when more than 5phr is not only the stability of the resin solution is lowered but the excessively injected unreacted epoxy resin to inhibit the coating film properties Because.

According to the present invention, when the above-mentioned first resin solution contains fluorine or fluorine-ethylene crab wax, a second resin solution having improved blackening property after processing can be obtained. At this time, the content of the fluorine or fluorine-ethylene wax contained is preferably 2-20phr, the reason is that less than 2phr blackening after processing, and more than 20phr impaired the coating film adhesion to the coating film on the top Because it becomes.

Hereinafter, a method for producing a resin coated steel sheet in which a resin coated layer is formed on the chromate-treated electrogalvanized steel sheet with the first resin solution or the second resin solution will be described.

First, the first resin coating solution or the second resin solution is applied onto the galvanized steel sheet, and the coating thickness thereof is preferably such that the thickness after baking is 0.5-3.0 μm. The reason is that when the film thickness is less than 0.5 μm, the film thickness is thin and it is difficult to secure sufficient physical properties. When it exceeds 3.0 μm, the chemical resistance is not affected by the increase in the film thickness.

Subsequently, the steel sheet on which the resin film is formed is baked as described above, and the temperature at this time is preferably 80-180 ° C. If the baking temperature is below 80 ℃, the curing reaction of the resin is not enough, and the physical properties of the coating film are lowered. On the contrary, if the baking temperature is higher than 180 ℃, the curing reaction does not occur any more and the calorie loss is so large.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1

The resin synthesis was performed by adding 10 parts of an ethylene-acrylic copolymer resin having a number average molecular weight of 50,000 in the form of dispersed in water in a four-necked flask and adding a hydrogen group to 20 nm of cloidal silica with respect to the resin. A silica-modified ethylene-acrylic copolymer resin was prepared by stirring a 150 phr, gamma-glycidoxypropyltrimethoxysilane, which is a silane coupling agent, with 1 phr to the resin at 70 ° C. for about 3 hours, followed by cooling. ) In this main solution, various kinds of epoxy resins having different molecular weights were dispersed in water to obtain a resin solution for anti-fingerprint in various amounts.

In the manufacture of thin-film resin-treated steel sheet, after coating the above-mentioned resin solution on a chromate-treated zinc electroplated steel sheet having zinc deposition amount and chromium deposition amount of 20 g / m 2 and 50 mg / m 2, respectively, the steel sheet temperature was baked at 120 ° C. and then water cooled. After preparing a resin coated steel sheet having a dry resin coating thickness of 1 μm, the adhesive pickup material generation degree and roll cleaning property, solution stability, and chemical resistance were evaluated on the roll as follows, and the results are shown in Table 1 below. It was.

First, the occurrence of sticky pickup material on the roll was evaluated in five steps as follows.

◎: No sticky pickup material generated when working for 6 hours or more

○: Sticky pickup material generated after 6 hours of operation

□: Sticky pickup material generated during 4-5 hours of operation

△: Adhesive pickup material generated when working for 4 hours or less

Ｘ: Adhesive pickup material generated when working for 3 hours or less

2) Roll cleaning was evaluated in three stages as follows.

◎: Easy cleaning, no sticky residue

□: Easy to clean but sticky residue

Ｘ: poor cleanability and sticky residue

3) Chemical resistance was evaluated by dividing the degree of peeling and discoloration of resin coating film into 5 grades when rubbing the coating film with MEK. The evaluation criteria are as follows.

(Double-circle): Color difference (contrast color difference before a process) (DELTA) E 1 or less, without peeling of resin coating film

(Circle): Color difference (contrast color difference before processing) △ E 2-3

□: No peeling of resin film and color difference (compared to color difference before treatment) △ E 5 or more

(Triangle | delta): Partial peeling of resin coating film (The peeling part is 30% or less of resin conductive cloth surface.)

Ｘ: Complete peeling of resin coating film (more than 50% of the surface of resin conductive cloth)

4) The solution stability (storability) was evaluated by dividing the degree of change in the viscosity of the solution for 30 days at 35 ° C into 5 grades.

◎: Viscosity change range of solution is 2 cps or less

(Circle): The viscosity change range of a solution is 2-4cps

□: Viscosity change of solution is 4-6cps

(Triangle | delta): The viscosity change range of a solution is 6-8cps

Ｘ: Viscosity change of solution is more than 10cps

Solution composition change Quality assessment Hardener Roll non-sticky Roll Cleanability Chemical resistance Solution stability Kinds Molecular Weight Content (phr) Comparative material One Silica Modified Ethylene-Acrylic Resin Epoxy resin - 0 ◎ ◎ Ｘ ◎ 2 380 One □ □ △ ◎ 3 3 Ｘ Ｘ ◎ ◎ 4 5 Ｘ Ｘ ○ ◎ 5 10 Ｘ Ｘ □ △ 6 470 One □ □ △ ◎ 7 3 Ｘ Ｘ ◎ ◎ 8 5 Ｘ Ｘ ○ ◎ 9 10 Ｘ Ｘ □ △ 10 900 One ◎ ◎ □ ◎ Invention One 3 ◎ ◎ ◎ ◎ 2 5 ◎ ◎ ◎ ◎ Comparative material 11 10 ◎ ◎ △ □ 12 1500 One ◎ ◎ □ ◎ 13 3 ◎ ◎ □ ◎ 14 5 ◎ ◎ □ ◎ 15 10 ◎ ◎ △ □

As shown in Table 1, it was shown that solution stability was deteriorated as the epoxy content was increased, and chemical resistance was deteriorated even though the epoxy resin content was increased when the epoxy resin molecular weight was less than 900. 10)). In addition, when the content of the epoxy resin as a curing agent was 1% by weight, the occurrence of sticky pickup was small, and the water washing performance was good, but the chemical resistance was insufficient (Comparative Materials (2, 6, 10, 12)). In addition, even when the content of the epoxy resin, which is a curing agent, exceeds 5% by weight, the adhesive pickup and water washing were good, but the chemical resistance was deteriorated due to the unreacted curing agent due to the excessive addition of the curing agent (Comparative Materials (5, 9, 11). , 15)).

Example 2

After adding a curing agent and wax to the silica-modified ethylene-acrylic resin of Example 1 under the conditions of Table 2 below, the coefficient of friction, blackening after processing, and coating film adhesion were evaluated as follows, and the results are shown in Table 2 below. It was.

1) Machinability evaluation was measured by the planar friction coefficient, which was measured by the condition of equation (1) cut into 45x300mm specimen, and the pressure applied to the specimen was 0.27kg / ㎠, drawing speed sms was set to 1,000 mm / min.

Coefficient of friction (μ) = F _d / F _n ... (1)

F _d : Drawing Force, F _n : Normal Force

2) The blackening evaluation method after machining was to evaluate the surface coefficient of the specimen after measuring the friction coefficient and the evaluation criteria are as follows.

◎: Color difference between friction coefficient evaluation surface and surface before evaluation △ E 0.5 or less

○: Color difference between the friction coefficient evaluation surface and the surface before evaluation ΔE 0.5-1.0

□: Color difference between friction coefficient evaluation surface and surface before evaluation △ E 1.0-1.5

Δ: color difference between the friction coefficient evaluation surface and the surface before evaluation ΔE 1.5-2.0

Ｘ: Color difference △ E 2.0 or more between the friction coefficient evaluation surface and the surface before evaluation

3) Film adhesion is the baking of Melamine-Alkyd for 150 ℃ x20 minutes, and the top coat is dried to 20㎛. After that, check boards are made at intervals of 1mm, and then a certain pressure is applied. The evaluation criteria are as follows.

◎: Top coat peeling area (less than 0%)

○: Top coat peeling area (0-10%)

□: Top coat peeling area (10-30%)

△: Top coat peeling area (30-50%)

Ｘ: Top coat peeling area (50-100%)

division Solution composition change Quality evaluation result Topical solution Hardener Wax * Coefficient of friction Blackening after processing Coating Film Adhesion Kinds Content (phr) Comparative material 16 Silica Modified Ethylene-Acrylic Resin Epoxy Resin 3phr With Molecular Weight 900 - 0 0.251 Ｘ Good 17 Ethylene 10 0.124 △ Good 18 20 0.083 ◎ Bad 19 Propylene 10 0.138 △ Good 20 20 0.091 ◎ Bad 21 Ethylene-propylene copolymer 10 0.102 ○ Good 22 20 0.071 ◎ Bad 23 Fluorine-Ethylene Copolymer 0.5 0.211 □ Good 24 One 0.185 ○ " Invention 3 2 0.099 ◎ " 4 5 0.081 ◎ " 5 10 0.074 ◎ " 6 15 0.069 ◎ " 7 18 0.063 ◎ " Comparative material 25 20 0.059 ◎ Bad *: Wax is good for added solution 100. ← ◎, ○, □, △, Ｘ → Poor

As shown in Table 2, as the wax content increased, the friction coefficient decreased, but as the added amount increased, the adhesion to the top coat surface decreased. In addition, in the case of ethylene-based and propylene-based waxes, the blackening property is increased, but the coating film adhesion tends to be decreased, whereas in the case of fluorine-ethylene wax, the coating film adhesion is excellent, and the blackening property is significantly increased after processing.

Example 3

In Example 2, the resin solution prepared under the condition of Inventive Material (4) in Table 2 was prepared in the same manner as in Example 1, followed by evaluation of corrosion resistance, and the results are shown in FIG. 3. At this time, the corrosion resistance was evaluated by dividing the flat plate and the processed part by using the salt spray tester.The flat plate was loaded into the salt spray tester as it was in the specimen. Washed with pure water, dried, and evaluated as white rust generated.

As shown in FIG. 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. On the contrary, when the thickness is 3.0 μ or more, the resin film is detached during processing and the corrosion resistance of the processed part is lowered.

As described above, according to the present invention, it is possible to prevent sticky pickup of the resin component on the coating roll, thereby improving the surface quality of the resin-treated steel sheet product, extending the service life of the roll, and reducing equipment downtime for replacing the roll, and solution. It is possible to expect the effect of reducing the environment and cost by carrying over the residual amount of resin after working to secure storage property without wastewater treatment and improving the processability of steel sheet, which can contribute to the resolution of customer's complaints considerably.

Claims (3)

In the resin solution applied to the chromate-treated electrogalvanized steel sheet, Ethylene-acrylic resin is a mixture of ethylene-acrylic resin and silica: 10-20phr, silane coupling agent: 0.1-3phr Resin solution with excellent workability, solution stability and blackening after processing. In the resin solution applied to the chromate-treated electrogalvanized steel sheet, Epoxy resin with a molecular weight of 900 or more and less than 1500, based on ethylene-acrylic resin mixed with silica: 10-20 phr and silane coupling agent: 0.1-3 phr: 3-5 phr and fluorine or fluoroethylene wax: Resin solution with excellent workability, solution stability and blackening after processing, characterized by containing 2-20phr. In the manufacturing method of the resin coated plated steel sheet which uses the chromate-treated electrogalvanized steel sheet as a base steel plate, and forms a resin coating layer thereon, The resin coated steel sheet is characterized in that the coated steel sheet is applied to a dry film thickness of 0.5-3.0 μm using the resin solution of claim 1 or 2 on the base steel sheet, followed by baking the applied steel plate at 80-180 ° C. Way.

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