KR101899644B1 - Method for manufacturing coated steel sheet having heat insulating property - Google Patents

Abstract

The present invention relates to a method for preparing a coating solution, which comprises preparing a coating solution for preparing a coating solution containing thermally expandable particles of a core shell structure containing a hydrocarbon as a core material and a binder resin in a shell made of a thermoplastic resin, A heat treatment step of heat treating the coating solution to form a heat insulating coating layer, and a step of forming a top coating layer on the heat insulating coating layer. According to the method, It is possible to obtain an excellent heat insulating property even if a thin film coating is applied by using the particles, and it is possible to form a thin film coating by a roll-to-roll method, so that a heat insulating steel sheet can be manufactured easily and economically have.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for manufacturing a coated steel sheet having heat insulating properties,

The present invention relates to a method of manufacturing a coated steel sheet having an adiabatic property that can be used for automobiles, building materials, home appliances, and the like.

As energy costs are increasing due to high oil prices, there is a growing demand for energy saving technologies throughout the industry.

Steel plates are widely used for automobiles, building structures, and exterior materials for electronic products because they are cheap and have good processability. However, steel plates generally have a high thermal conductivity and thus have poor thermal efficiency, which is an unfavorable material in terms of energy saving.

On the other hand, adiabatic paints developed for the general industry such as Patent Documents 1 and 2 are produced by combining simple hollow particles and heat insulating particles. It is difficult to secure a sufficient heat insulating effect (low thermal conductivity) even when applied to a steel sheet material. In order to obtain a sufficient heat insulating effect, the coating layer of the paint must be thicker than about 500 탆. However, such a thick coating layer is not only excellent in processability but also difficult to coat in a roll-to-roll process of steel sheet production.

The more the air contained in the particles used for forming the heat insulating coating layer, the better the heat insulating performance can be secured. Therefore, it is necessary to use a hollow particle having a large particle size and a small thickness as the heat insulating coating particle in a hollow form in order to secure a high heat insulating performance. However, in order to obtain a sufficient heat insulating effect by using such heat-insulating coating particles, there is a problem that a coating layer must be a thick film having a thickness of 500 탆 or more.

Therefore, it is necessary to continuously research and develop a heat-insulating coated steel sheet capable of securing sufficient heat insulating performance and mass-producing it.

Korean Patent No. 10-0816085 Korean Patent No. 10-0918085

In one embodiment, the present invention provides a method for producing a coated steel sheet that is easy to manufacture and has excellent adiabatic properties.

According to an embodiment of the present invention, there is provided a method for producing a coating solution, comprising the steps of: preparing a coating solution for preparing a coating solution containing thermally expandable particles of a core shell structure containing hydrocarbon as a core material inside a shell made of a thermoplastic resin; A method for producing a coated steel sheet having adiabatic properties, comprising the steps of: applying a solution to a surface of a steel sheet; heat-treating and curing the coating solution to form a thermal coating layer; and forming a top coating layer on the thermal- to provide.

The heat treatment can be performed within a temperature range of the maximum expansion temperature (T) of the thermal expansion particles ± 20 ° C.

The curing step may include a semi-curing heat treatment of the coating solution to form a semi-cured adiabatic coating layer, and a complete curing heat treatment of the semi-cured coating layer to form a cured heat-insulating coating layer.

The semi-curing heat treatment may be performed at a temperature not lower than a curing initiation temperature of the coating solution and a maximum expansion temperature (T) of the thermal expansion particles being less than -20 ° C.

The complete curing heat treatment can be performed within a temperature range of the maximum expansion temperature (T) of the thermal expansion particles ± 20 ° C.

And a top coating layer may be formed on the semi-cured, heat-insulating coating layer.

The cured heat insulating coating layer and the top coating layer can be simultaneously subjected to complete curing heat treatment.

The curing step may include a step of semi-curing the coating solution to form a semi-cured adiabatic coating layer, and a step of forming a cured adiabatic coating layer by irradiating ultraviolet (UV) to the semi-cured coating layer.

 The semi-curing heat treatment may be performed at a temperature not lower than the curing initiation temperature of the coating solution, and at a temperature at which the maximum expansion temperature (T) of the thermal expansion particles is less than -20 ° C.

And a top coating layer may be formed on the semi-cured, heat-insulating coating layer.

 The cured heat-insulating coating layer and the top coating layer can be completely cured simultaneously by irradiating ultraviolet rays.

The heat expandable particles may be a shell of an acrylonitrile resin, an acrylonitrile copolymer resin or a styrene resin.

The thermal expansion particles may have a diameter size of 20 to 1000 탆 at the maximum expansion temperature.

The thermal expansion particles may be contained in an amount of 1 to 20% by weight based on the total weight of the solid content of the coating solution.

The binder resin may be at least one selected from the group consisting of polyester resin, polyepoxy resin, fluorine resin, polyurethane resin, acrylic dispersion resin, alkyd resin, acrylic emulsion, acrylic silicone emulsion, urethane emulsion, fluorine emulsion, silicone inorganic resin, A hybrid resin, a UV binder resin, and an acrylic binder resin.

The coating solution can be fully cured within a temperature range of the maximum expansion temperature of the heat expandable particles ± 20 ° C.

According to the present invention, by using the thermal expansion particles, it is possible to secure excellent heat insulating properties even when a thin film coating is applied, and it is possible to form a thin film coating by a roll-to-roll method, Can be manufactured.

FIG. 1 is a view schematically showing the concept of expansion and contraction behavior according to heat supply of the thermal expansion particles of the present invention. FIG.
2 is a graph schematically showing the volume expansion ratio of the thermally expandable particles according to the present invention.
FIG. 3 is a view schematically showing a shape in which thermal expansion particles are distributed on / off due to expansion of thermal expansion particles thicker than the coating layer thickness during heat treatment of the thermal insulation coating layer.
FIG. 4 is a schematic view showing a concept of forming a top coating layer on the surface of the heat-insulating coating layer, as an example of a method of manufacturing the heat-insulating coated steel sheet of the present invention.
FIG. 5 is a view schematically showing a process of forming a heat insulating coating layer by a semi-curing heat treatment and a full hardening heat treatment of a coating solution, as an example of a method of manufacturing the heat insulating coated steel sheet of the present invention.
FIG. 6 is a view schematically showing a process of forming a heat-insulating coating layer by semi-curing heat treatment and UV irradiation of a coating solution, as an example of a method of manufacturing the heat-insulating coated steel sheet of the present invention.
Figs. 7 and 8 are schematic views exemplarily showing processes and equipments for producing the heat-insulating coated steel sheet of the present invention.
9 is a SEM photograph of a section of the coated steel sheet obtained in Example 2. Fig.
10 is a temperature profile obtained by measuring the temperature change measured on the back surface of the specimen under a heat source.
11 is a photograph of the surface and cut section of Example 8 taken by an electron microscope.
12 is a photograph of the surface and cut section of Example 9 taken by an electron microscope.
13 is a photograph of the surface and cut section of Comparative Example 4 taken by an electron microscope.
14 is a photograph of the surface and cut section of Comparative Example 5 taken by an electron microscope.

Hereinafter, preferred embodiments of the present invention will be described with reference to various embodiments. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below.

The present invention relates to a method for manufacturing a heat-insulating coated steel sheet which can be used for automobiles, building materials, home appliances, etc., and in order to secure excellent heat insulating properties, the size of the heat- I will.

The inventors of the present invention have confirmed that even when the thickness of the coating layer is made thinner when the heat expandable particles having thermal expanding properties are used as the heat insulating particles, it is possible to secure the heat insulating property at least equal to that of the conventional heat- .

Hereinafter, the present invention will be described in detail.

According to the present invention, there is provided a method for producing a steel sheet excellent in thermal insulation characteristics, comprising the steps of: preparing a coating solution containing thermal expansion particles; applying the coating solution to the surface of a steel sheet; Forming a coating layer, and forming a top coating layer on the heat insulating coating layer.

As shown in FIG. 1, the thermo-expandable microcapsule used in the present invention is a hollow structure including a hydrocarbon as a core material and a thermoplastic resin shell.

As shown in FIG. 1, when the heat expandable particles are heated, the shell of the particles softens and changes into an expandable state, and the internal hydrocarbons are gasified to increase the internal pressure of the heat expandable particles, Thereby expanding the volume of the bag. If the temperature exceeds the maximum swelling temperature of the thermally expandable particles, the internal hydrocarbons will all escape to the outside and the shell will collapse due to heat. The rate of expansion of the thermally expanded particles according to the temperature is shown in FIG. 2, and it can be understood from this.

The present invention relates to a method for manufacturing a heat-insulating coated steel sheet which can secure the heat insulating property by using the expansion characteristics of the thermally expandable particles, wherein the thermally expandable particles are made of a thermoplastic resin shell and a hydrocarbon ≪ / RTI >

The thermoplastic resin constituting the shell of the heat expandable particles is not particularly limited as long as it is heat-expandable and can be suitably used in the present invention. For example, acrylonitrile copolymer, vinylidene chloride or polystyrene resin, . These thermal expansion particles can be appropriately selected according to the temperature range required in the application to which the steel sheet having the coating layer formed therein is applied.

The thermal expansion particles include liquid hydrocarbons. The hydrocarbon vaporizes inside the thermally expandable particles in accordance with the applied heat to increase the internal pressure of the thermally expandable particles, thereby expanding the thermoplastic resin constituting the shell of the thermally expandable particles. The vaporized internal hydrocarbon gas may block the transfer of external heat and provide an adiabatic effect.

The liquid hydrocarbon contained in the thermally expandable particles is not particularly limited, but may be suitably used as long as it is present in a liquid state at room temperature and has a characteristic of vaporizing when heated, for example, octane.

The size of the thermally expandable particles is not particularly limited in terms of the size of the thermally expandable particles at the maximum thermal expansion temperature. The size of the thermal expansion particles in the coating film can be controlled by controlling the curing temperature at the time of curing, so that the size of the thermal expansion particles is not a problem. However, for example, those having a thickness of 20 to 1000 mu m can be used.

By coating the surface of the steel sheet with a coating solution containing the above-mentioned thermally expandable particles, the heat insulating property of the steel sheet can be improved. The coating solution to be coated on the surface of the steel sheet is not particularly limited. The coating solution may be water-soluble or pulverulent and is not particularly limited.

At this time, the thermal expansion particles may be contained in an amount of 1 to 20% by weight based on the total weight of the solid content of the coating solution. In order to secure the adiabatic property to be achieved in the present invention, the content of the thermal expansion particles is preferably 1 wt% or more. When the content of the thermal expansion particles exceeds 20 wt% based on the total solid content of the coating solution, The volume of the particles in the coating layer exceeds 80% when the expanding particles are fully expanded, resulting in poor physical properties of the coating film.

The prepared coating solution is applied to the surface of the steel sheet. The steel sheet may be a steel sheet to which a heat-insulating coated steel sheet such as an automobile, an electric appliance or a building can be applied, and the kind thereof is not particularly limited.

In applying the coating solution containing the thermal expansion particles on the steel sheet, the coating method is not particularly limited. For example, various methods such as roll coating, spraying, and dipping can be applied. If high-speed production is desired, the surface of the steel sheet can be coated by a roll coating method.

The coating may have a thickness of the coating layer of 10 mu m or more. In order to produce a steel sheet having the heat insulating property of the present invention, it is preferable that a coating layer is formed to a thickness of at least 10 탆. However, the upper limit is not particularly limited, and may be, for example, 500, 300, 100, or 70 탆. However, the present invention is desirably 40 탆 or less in that the coating layer can have adiabatic characteristics even when the thickness of the coating layer is made thin.

After applying the coating composition containing the thermal expansion particles of the present invention, the heat-treated coating layer is formed by curing the steel sheet on which the coating layer is formed by heat treatment. At this time, it is preferable that the heat treatment is performed at a temperature near the maximum expansion temperature of the heat expansion particles. More specifically, it is preferable that the heat expansion temperature is in the range of the maximum expansion temperature (T) ± 20 ° C. By performing the heat treatment in the temperature range as described above, it is possible to secure the heat insulating property of the heat insulating coating layer formed on the steel sheet.

1 and 2, contraction occurs at a heat treatment temperature that is too high based on the maximum expansion temperature T of the thermally expanded particles, and therefore, the maximum expansion temperature T does not exceed + 20 ° C . On the other hand, since it is difficult to secure a heat-insulating coating layer having a sufficient heat insulating effect at an excessively low heat treatment temperature, it is preferable to heat treat the film at a maximum expansion temperature (T) of -20 캜 or more, Is more preferable.

Therefore, the thermosetting temperature of the binder resin of the thermoplastic resin forming the shell of the heat expandable particles and the heat-insulating coating layer may be in a similar range. However, the kind of the binder resin is not particularly limited as long as the curing temperature can be controlled by the choice of the curing agent. Examples of the binder resin applicable to the present invention include polyester resins, polyepoxy resins, fluororesins, polyurethane resins, acrylic dispersion resins, alkyd resins, acrylic emulsions, acrylic silicone emulsions, urethane emulsions , UV-binder resins including fluorine-based emulsions, silicone inorganic resins, silica sol-based resins, organic-inorganic hybrid resins, acrylic monomers and oligomers, and acrylic binder resins such as MMA and MA. The kind of the binder resin is not particularly limited so long as it is a conventional binder resin used in the technical field.

Meanwhile, in the case of forming the heat insulating coating layer by expanding the thermal expansion particles by heat-treating the coating layer formed of the coating solution containing the thermal expansion particles according to the present invention, the thermal expansion particles are expanded Thereby increasing the volume. At this time, depending on the type of the thermoplastic resin constituting the shell of the thermally expanding particles, it can expand from several times to several tens of times. 3, the thermal expansion particles may expand to a thickness greater than the thickness of the coating layer, and when the thermal expansion particles expand more than the thickness of the coating layer, the thermal expansion particles may accumulate in the ellipsoidal coating layer There is a problem that it has a deformed shape. As a result, the adhesive force between the thermal expansion particles and the heat insulating coating layer is lowered, and the thermal expansion particles are eventually dropped, thereby deteriorating the heat insulating properties. Further, there is a fear that the thermal expansion particles in the heat insulating coating layer undergo rapid thermal expansion during thermal curing, thereby causing cracking of the coating layer.

Therefore, in order to prevent problems such as deterioration of adhesion between the thermal expansion particles and the heat insulating coating layer due to expansion of the thermal expansion particles to a thickness larger than the thickness of the heat insulating coating layer, according to one embodiment of the present invention, a top coating layer may be formed. As shown in FIG. 4, by forming the top coating on the upper layer of the heat insulating coating layer, it is possible to prevent the coating layer including the thermal expansion particles from falling off. Furthermore, such a topcoat layer can protect the coating particles from external scratches and the like. Further, after the thermal insulation coating, the ability to adhere to the upper coating layer when another kind of coating, such as, for example, .

Meanwhile, In order to prevent problems such as deterioration of adhesion between the thermal expansion particles and the heat-insulating coating layer due to expansion of the thermal expansion particles to a thickness larger than the thickness of the heat-insulating coating layer, according to one embodiment of the present invention, the coating solution is heat- After the semi-cured adiabatic coating layer is formed, the semi-cured coating layer may be completely cured to form a cured adiabatic coating layer. In order to prevent the thermal expansion particles from expanding to a thickness equal to or thicker than the heat insulating coating layer after coating the coating solution containing the thermal expansion particles on the surface of the steel sheet, the heat expansion treatment is first performed after full- It is possible to prevent the problems caused by the inward / outward deviation.

The concept of semi-cured adiabatic coating layer formation for semi-curing heat treatment is schematically shown in Fig. As shown in FIG. 5, since the coating layer is semi-cured by the semi-curing heat treatment, the movement of the thermal expansion particles can be suppressed even after the heat treatment is performed near the maximum expansion temperature for complete curing. In addition, when the semi-cured heat treatment is performed, the coating composition is relatively viscoelastic as compared with the case where the coating composition is fully cured to 100%, which is preferable because it can reduce the damage of the coating film when the thermal expansion particles swell.

Preferably, the semi-curing heat treatment is performed in a temperature range that prevents the thermal expansion particles from expanding to a thickness equal to or thicker than the heat insulating coating layer. For example, the semi-curing heat treatment is performed at a temperature higher than the curing start temperature of the coating solution, ) -20 < 0 > C. If the semi-cured heat treatment temperature is less than the maximum thermal expansion temperature (T) of the thermal expansion particles (T) -20 ° C, the thermal expansion particles expand to a thickness equal to or thicker than the thermal insulation coating layer, .

The semi-cured heat-insulating coating layer, which is semi-cured heat-treated at a temperature not lower than the curing initiation temperature of the coating solution and in a temperature range of the maximum expansion temperature (T) of the thermal expansion particles is less than -20 ° C, 60%. At this time, the semi-cured adiabatic coating layer is viscous and sticky, and has viscoelasticity higher than that of fully cured, so that it is possible to reduce the damage of the coating film when the thermally expandable particles expand.

The heat insulating coating layer can be formed by performing a semi-curing heat treatment on the coating solution applied to the surface of the steel sheet, followed by a complete curing heat treatment for completely curing the semi-cured heat insulating coating layer.

It is preferable that the full-hardening heat treatment does not exceed the maximum expansion temperature (T) + 20 占 폚, because shrinkage occurs at a heat treatment temperature that is too high based on the maximum expansion temperature (T) of the thermal expansion particles. On the other hand, since it is difficult to secure a heat-insulating coating layer having a sufficient heat insulating effect at an excessively low heat treatment temperature, it is preferable to heat treat the film at a maximum expansion temperature (T) of -20 캜 or more, Is more preferable.

As described above, it is possible to form the top coating layer after forming the heat insulating coating layer by the heat treatment, and even when the heat-curing coating layer is formed by completely curing the semi-cured coating layer after the semi-curing heat treatment as described above, A top coating layer can be formed. By forming the top coating layer in this manner, it is possible to prevent the heat insulating coating layer from falling off and protect the coating particles from external scratches or the like. Further, after adiabatic coating, it is possible to increase the ability to adhere to the upper coating layer when another kind of coating such as, for example, a color coating treatment is performed.

According to another embodiment of the present invention, a semi-cured adiabatic coating layer may be formed by semi-curing the coating solution, and then a top coating layer may be formed on the semi-cured adiabatic coating layer. Thereafter, the semi-cured adiabatic coating layer and the top coating layer may be completely cured.

At this time, the top coating layer is not particularly limited, but it is preferable to use a solution having the same composition as the thermal coating solution, except that it does not contain thermal expansion particles. That is, the top coating layer can improve the bonding force between the top coating layer and the heat insulating coating layer by forming a top coating layer with a coating composition containing the same kind of resin as the binder resin of the heat insulating coating layer.

The thickness of the top coating layer is not particularly limited as long as it can prevent the thermal expansion particles from being exposed and peeled off. For example, the thickness is 10 占 퐉 or more, 10 占 퐉 to 50 占 퐉, 10 to 30 占 퐉, 40 占 퐉, 10 to 30 占 퐉, and the like.

According to an embodiment of the present invention, in order to prevent problems such as deterioration of adhesion between the thermal expansion particles and the heat-insulating coating layer due to expansion of the thermal expansion particles to be thicker than the thickness of the heat-insulating coating layer, the coating solution is heat- After forming the heat-insulating coating layer, ultraviolet rays (UV) may be applied to the semi-cured coating layer to form a fully cured heat-insulating coating layer. In order to prevent the thermal expansion particles from expanding to a thickness equal to or thicker than the heat insulating coating layer after coating the coating solution containing the thermal expansion particles on the surface of the steel sheet, the thermally expandable particles are irradiated with UV light after being semi- It is possible to prevent a problem caused by the occurrence of the defect.

The concept of formation of the heat-insulating coating layer by UV irradiation is schematically shown in Fig. As shown in Fig. 6, the thermal expansion particles are expanded by the semi-curing heat treatment, and the coating layer in the semi-cured state suppresses the movement of the expanded thermal expansion particles, thereby preventing the problem of being unevenly distributed on the coating layer. In addition, when the semi-cured heat treatment is performed, the coating composition is relatively viscoelastic as compared with the case where the coating composition is fully cured to 100%, which is preferable because it can reduce the damage of the coating film when the thermal expansion particles swell.

Preferably, the semi-curing heat treatment is performed in a temperature range that prevents the thermal expansion particles from expanding to a thickness equal to or thicker than the heat insulating coating layer. For example, the semi-curing heat treatment is performed at a temperature higher than the curing start temperature of the coating solution, ) -20 < 0 > C. If the semi-cured heat treatment temperature is less than the maximum thermal expansion temperature (T) of the thermal expansion particles (T) -20 ° C, the thermal expansion particles expand to a thickness equal to or thicker than the thermal insulation coating layer, .

The semi-cured heat-insulating coating layer, which is semi-cured heat-treated at a temperature not lower than the curing initiation temperature of the coating solution and in a temperature range of the maximum expansion temperature (T) of the thermal expansion particles is less than -20 ° C, 60%. At this time, the semi-cured adiabatic coating layer is viscous and sticky, and has viscoelasticity higher than that of fully cured, so that it is possible to reduce the damage of the coating film when the thermally expandable particles expand.

A completely cured heat-insulating coating layer can be formed by irradiating ultraviolet rays (UV) onto the semi-cured heat-insulating coating layer after the semi-cured heat-insulating coating layer is formed by semi-curing heat treatment of the coating solution applied to the surface of the steel sheet.

As described above, not only can the top coating layer be formed after forming the heat insulating coating layer by the heat treatment, but also when the completely cured heat insulating coating layer is formed by irradiating UV to the semi-cured coating layer after the semi-curing heat treatment as described above, A top coating layer may be formed on the coating layer. By forming the top coating layer in this manner, it is possible to prevent the heat insulating coating layer from falling off and protect the coating particles from external scratches or the like. Further, after adiabatic coating, it is possible to increase the ability to adhere to the upper coating layer when another kind of coating such as, for example, a color coating treatment is performed.

According to another embodiment of the present invention, a semi-cured adiabatic coating layer may be formed by semi-curing the coating solution, and then a top coating layer may be formed on the semi-cured adiabatic coating layer. Then, the semi-cured adiabatic coating layer and the top coating layer can be completely cured simultaneously by irradiating UV.

On the other hand, since the binder resin contained in the heat-insulating coating layer and the top coating layer can be completely cured when irradiated with ultraviolet rays, it is preferable to use an ultraviolet curable binder resin. The specific kind of the binder resin is not particularly limited as long as it is cured by ultraviolet rays.

In the coating solution for forming the heat-insulating coating layer of the present invention, the kind of the binder resin contained in the coating solution is not particularly limited, and any binder resin may be suitably used in the present invention as long as it can be thermally cured in the heat treatment temperature range described above . Since the thermosetting temperature of the resin is usually influenced by the curing temperature of the curing agent used for thermal curing of the resin, it is more preferable that the curing agent has a maximum expansion temperature (T) of ± 20 ° C Those having a curing property in a temperature range can be suitably used.

The curing agent can be cured within the range of the maximum expansion temperature (T) ± 20 ° C. of the thermal expansion particles contained in the thermal insulation coating solution, and the curing can be initiated at a temperature lower than the maximum expansion temperature (T) It is preferable to use a material which can be semi-hardened. As a result, the coating solution can be fully cured within the temperature range of the maximum expansion temperature of the thermal expansion particles ± 20 ° C.

As the kind of the curing agent, any of those having the above characteristics can be used. For example, amine curing agent, block isocyanate curing agent and the like can be used, and various known or commercially available curing agents can be suitably selected Can be used.

FIG. 6 schematically shows a step of forming the heat-insulating coating layer of the present invention on a steel sheet. The method of forming the heat-insulating coating layer is not particularly limited. As shown in FIG. 6, a roll-to-roll method may be used after optional thermal curing heat treatment, Forming a top coating layer, and the like can be continuously performed, thereby improving the productivity of the heat-insulating coated steel sheet.

For example, FIG. 7 schematically shows a process of performing a heat-seal coating layer according to an embodiment of the present invention by a roll-to-roll method. 7, the coating solution was coated on the surface of the steel sheet (1st roll coating), followed by semi-curing heat treatment or curing heat treatment (first baking) to form an adiabatic coating layer, followed by coating the top coating composition coating can be cured by heat treatment (2nd baking).

According to the present invention, in the formation of the heat insulating coating layer on the surface of the steel sheet, thermal expansion particles are included in the heat insulating coating composition, and the coating layer is formed in a state in which the thermal expansion particles are thermally expanded during the formation of the coating layer, Therefore, even when the thickness of the coating layer is made thin, excellent heat insulation can be ensured.

That is, as compared with the heat-insulating coating layer formed of the coating composition that does not include the thermal expansion particles of the present invention, it is possible to improve the heat insulating effect in that a better effect can be obtained in the heat- The thickness of the coating layer can be made thin.

In addition, in the heat-insulating coating layer containing the thermal expansion particles of the present invention, it is possible to realize the heat insulating property even with a small amount of thermal expansion particles. That is, even if only 20% of the total solid content includes the thermal expansion particles, it occupies about 80% of the volume after the thermal expansion, thereby maximizing the heat insulation efficiency compared to the case where the conventional preformed particles are charged .

Further, according to the present invention, even if the steel sheet is applied to a pre-formed steel sheet, the heat insulating property can be improved while maintaining corrosion resistance and workability.

Hereinafter, the present invention will be described in more detail with reference to examples. The following examples are intended to further illustrate the present invention and are not intended to limit the present invention.

Example

1. Evaluation of thermal insulation characteristics with and without thermal expansion particles

[Example 1]

1.45 g of a block isocyanate curing agent (BL-7982, Bayer material Science Desmodor) having a curing temperature of 180 to 250 캜, 20 g of ES 955 (SK Chemical Co., skyborn ES955, MW 12,000, polyester resin high porosity type) 0.19 g of butyltin dilaurate and K150 (SK Chemical Co., Ltd.) as a solvent. Thermal expansion particles F190D (Matsumoto, thermal expansion particles containing octane in an acrylonitrile polymer resin shell, maximum expansion temperature: 210 to 220 (Diameter at the maximum expansion: 180 to 240 占 퐉) in an amount of 6% by weight (based on solid content).

The coating solution was coated on the surface of a zinc-plated steel sheet (0.6 mm thick) by a roll-to-roll method to a thickness of 15-40 탆. The steel sheet coated with the coating solution was heat-treated at 215 캜 to form a heat-insulating coating layer having a thickness after swelling of 60 to 200 탆.

A top coating composition comprising 20 g of ES955, 1.45 g of BL-7982 and 0.1 g of dibutyltin dilaurate and K150 (solvent) was applied on the heat insulating coating layer to a thickness of 12-20 탆. The steel sheet coated with the top coating composition was heat-treated at 225 to produce a heat-coated steel sheet having a top coating layer.

The cross section of the steel sheet thus formed was photographed by SEM photographs, and the results are shown in Fig.

[Comparative Example 1]

A coating solution (solvent borne clear) having the same composition and composition as the coating solution of Example 1 but not containing thermal expansion particles was prepared.

The coating solution was coated on the surface of a zinc-plated steel sheet (thickness 0.6 mm) by a roll-to-roll method to a thickness of 15-40 탆, and the steel sheet coated with the coating solution was heat-treated at 220 캜 to form a heat insulating coating layer.

The heat insulating properties were confirmed for Example 1 and Comparative Example 1. The heat insulation property was measured by measuring the temperature of the back surface of the specimen while increasing the temperature of the specimen by heating the specimen with the IR lamp as a heat source, and measuring the temperature change with time, and the temperature profile was shown in FIG.

As shown in Fig. 9, Example 1 including the thermally expanding particles was confirmed to have significantly superior adiabatic properties as compared with Comparative Example 1.

2. Evaluation of adhesion according to 2-Baking step

[Examples 2 to 7]

A coating solution having the same composition and composition as the coating solution and the top coating composition of Example 1, but containing 10 wt% (based on solids) of F190D was prepared.

The coating solution is coated on the surface of a zinc-plated steel sheet (thickness 0.6 mm) by a roll-to-roll method to a thickness of 15-40 탆, a semi-cured heat treatment is performed on the steel sheet coated with the coating solution, . At this time, the semi-cured heat treatment temperature and the fully cured heat treatment temperature are shown in Table 1 below.

Then, a top coating layer as in Example 1 was formed on the heat insulating coating layer to prepare a heat insulating coated steel sheet.

[Comparative Examples 2 and 3]

A coating solution having the same composition and composition as the coating solution and top coating composition of Example 1, but containing 10 wt% of F190D, was prepared.

The coating solution was coated on the surface of a zinc-plated steel sheet (thickness: 0.6 mm) by a roll-to-roll method to a thickness of 15 to 40 탆, and the steel sheet coated with the coating solution was heat-treated at a temperature shown in Table 1 to form a heat- Respectively.

Then, a top coating layer as in Example 1 was formed on the heat insulating coating layer to prepare a heat insulating coated steel sheet.

division. Hardening method Heat treatment temperature (캜) Thermal insulation coating layer thickness (탆) Adhesiveness Example 2 Induction thin film heating 170 → 225 45 to 50 3B Example 3 Induction thin film heating 185 → 225 45 ~ 56 3B Example 4 Induction thin film heating 195 → 225 45 ~ 56 2B Example 5 Hot air hardening 170 → 225 40 to 50 4B Example 6 Hot air hardening 185 → 225 45 to 55 4B Example 7 Hot air hardening 195 → 225 53 to 63 4B Comparative Example 2 Induction thin film heating 220 55 ~ 75 0B Comparative Example 3 Hot air hardening 220 80-130 1B

The coating method was a bar coater to simulate roll coating and a coating was applied using # 40 Bar. Two methods of curing were used: Induction oven applicable to POSCO and Heat convection oven applicable to POSCO steel.

In the case of a hot air curing device, the ambient temperature was set at 250 ° C for 1 minute. When the PMT temperature was changed, the curing temperature was lowered by using an inverter.

The coating thickness was measured using Portable coating measurement (Dualscope FMP20).

As can be seen from the above Table 1, Examples 2 to 7 using the 2-Step baking method were confirmed to have remarkably excellent adhesion to the coating film as compared with Comparative Examples 2 and 3. [ Particularly, when curing is performed using a hot-air curing apparatus, it is confirmed that the particles have an adhesion of 4B or more because of sufficient particle expansion time.

3. Adhesion evaluation by semi-curing heat treatment process and UV irradiation process

[Examples 8 and 9]

30 g of LR9000 (low viscosity isocyanate acrylate) from BASF, 10 g of ES955 (SK Chemicals, skyborn ES955, MW 12,000, polyester resin high porosity type), 3 g of HDDA (hexane-1,6-diol diacrylate) 4 g of Irgacure-184 (Ciba, 1-Hydroxy-cyclohexy-phenyl-ketone), 8 g of toluene and 10 wt% of F190D (based on solids content) ) Was prepared.

 The coating solution is coated on the surface of a zinc-plated steel sheet (thickness: 0.6 mm) by a roll-to-roll method to a thickness of 15 to 40 탆, semi-cured by heat treatment of the steel sheet coated with the coating solution, Thereby forming an adiabatic coating layer. At this time, the semi-cured heat treatment temperature is shown in Table 2 below.

Then, a top coating layer as in Example 1 was formed on the heat insulating coating layer to prepare a heat insulating coated steel sheet.

[Comparative Examples 4 and 5]

A coating solution having the same composition and composition as the coating solution and top coating composition of Example 1, but containing 10 wt% of F190D, was prepared.

The coating solution was coated on the surface of a zinc-plated steel sheet (thickness: 0.6 mm) by a roll-to-roll method to a thickness of 15 to 40 탆, and the steel sheet coated with the coating solution was heat-treated at a temperature shown in Table 2 to form a heat- Respectively.

Then, a top coating layer as in Example 1 was formed on the heat insulating coating layer to prepare a heat insulating coated steel sheet.

division Curing temperature (℃) Whether UV irradiation Thermal insulation coating layer thickness (탆) Whether the film is peeled off Example 8 195 O 45 X Example 9 215 O 80-100 X Comparative Example 4 195 X 30 O Comparative Example 5 215 X 25 O

Fig. 11 shows the surface and cut section of Example 6, Fig. 12 shows the surface and cut section of Example 9, Fig. 13 shows the surface and cut section of Comparative Example 4, Is photographed with an electron microscope.

As can be seen from Table 2 and Figs. 11 to 14, in Examples 8 and 9 cured by the semi-curing heat treatment and the ultraviolet irradiation process, it was confirmed that the film peeling did not occur and the film adhesion was remarkably excellent. On the other hand, in Comparative Examples 4 and 5, it was confirmed that peeling of the coating film occurred.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be obvious to those of ordinary skill in the art.

Claims (16)

Preparing a coating solution for preparing a coating solution containing a core-shell-shaped thermal expansion particle containing hydrocarbon as a core material and a binder resin in a shell made of a thermoplastic resin;
A coating step of coating the coating solution on the surface of the steel sheet;
A semi-curing step of semi-curing the coating solution to form a semi-cured adiabatic coating layer; And
A complete curing step of curing the semi-cured adiabatic coating layer by heat treatment or UV irradiation to form a completely cured heat-insulating coating layer
Wherein the coating film has a heat insulating property.
The method of claim 1, further comprising a top coating layer forming step of forming a top coating layer on the semi-cured adiabatic coating layer or the fully cured adiabatic coating layer.
delete The method for producing a coated steel sheet according to claim 1, wherein the semi-curing heat treatment is performed at a temperature not lower than a curing start temperature of the coating solution and a maximum expansion temperature (T) of the thermal expansion particles is less than -20 占 폚.
The method according to claim 1, wherein the heat treatment in the full curing step is performed within a temperature range of maximum expansion temperature (T) ± 20 ° C. of the thermal expansion particles.
delete 3. The method of claim 2, wherein the semi-cured adiabatic coating layer and the top coating layer are fully cured at the same time by heat treatment.
delete delete delete The method of claim 2, wherein the semi-cured adiabatic coating layer and the top coating layer are completely cured by irradiating ultraviolet rays.
The method for producing a coated steel sheet according to claim 1, wherein the thermal expansion particles have an adiabatic property, wherein the shell is an acrylonitrile resin, an acrylonitrile copolymer resin or a styrene resin.
The method for producing a coated steel sheet according to claim 1, wherein the thermally expandable particles have a diameter of 20 to 1000 占 퐉 at a maximum expansion temperature.
The method according to claim 1, wherein the thermal expansion particles are contained in an amount of 1 to 20% by weight based on the total weight of the solid content of the coating solution.
The method according to claim 1, wherein the binder resin is selected from the group consisting of a polyester resin, a polyepoxy resin, a fluororesin, a polyurethane resin, an acrylic dispersion resin, an alkyd resin, an acrylic emulsion, an acrylic silicone emulsion, a urethane emulsion, a fluorine emulsion, Wherein the inorganic filler is at least one selected from the group consisting of silica sol-based resin, organic-inorganic hybrid resin, UV binder resin, and acrylic binder resin.
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