KR101917471B1 - Composite steel sheet having excellent adhesion and method for preparing the same - Google Patents

Abstract

The present invention relates to a steel plate; And a polyamide resin layer formed on one side or both sides of the steel sheet, wherein the polyamide resin layer has 10 or more methylene groups in the repeating unit and the repeating unit is composed of all trans conformation To a composite steel sheet excellent in adhesion. INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a lightweight composite steel sheet which is excellent in adhesion with the steel sheet itself without using a separate adhesive layer.

Description

TECHNICAL FIELD [0001] The present invention relates to a composite steel sheet having excellent adhesion and a method of manufacturing the composite steel sheet.

The present invention relates to a composite steel sheet excellent in adhesion and a method for producing the same.

BACKGROUND ART In order to reduce carbon dioxide in exhaust gas in response to environmental regulations in the automobile manufacturing industry and to reduce fuel consumption of fossil fuel cars and battery consumption of electric vehicles, weight reduction of automobile bodies is continuously being promoted.

Particularly, in the case of parts such as doors, hoods and trunks, which can not be expected to be lighter in weight due to the application of existing automotive steel plates, automobile manufacturers can use aluminum, plastic, magnesium There is an increasing tendency to adopt nonferrous lightweight materials.

However, such non-ferrous lightweight materials are expensive and have a drawback in that the properties required in automobile manufacturing processes such as weldability and paintability are insufficient.

Further, there is a real problem that aluminum or magnesium is difficult to satisfy the strength required for use as an automobile material, and it is difficult to ensure workability for part processing.

In the case of steel sheets for automobiles, there are two methods for weight reduction of parts using thin steel sheets: P-doped low carbon steel, Bake Hardenable steel, Duel Phase Steel ) Are used to reduce the weight of components by reducing the thickness of parts.

However, if the thickness of the steel sheet is too small, the problem arises that the component stiffness is rather lowered, so that the thickness can not be lowered unlimitedly. Therefore, such a steel sheet for automobiles has limitations in terms of reducing the thickness and weight of components.

On the other hand, a laminate steel sheet including a core material having a low specific gravity such as a plastic material between soft steel sheets can minimize the thickness of the soft steel sheet compared to the core material, thereby achieving weight reduction.

In particular, the laminated steel sheet is produced by applying an adhesive on a cold-rolled steel sheet or a coated steel sheet, passing a drying furnace at a predetermined temperature for a predetermined time, and applying a soft and hard polyvinyl chloride (PVC) film to the upper surface of the steel sheet And adhered while being squeezed by the pressure of the roll.

Such a laminate method is used as a material having enhanced design and high quality compared with a conventional metal coating, and has a merit that a large amount of products can be produced in less time than a metal coating.

On the other hand, as a material for a plastic film to be adhered to a steel sheet, for example, polyvinyl chloride has conventionally been used widely and has been used. A laminate steel sheet using a polyolefin film as a substitute material having a performance equivalent to that of the polyvinyl chloride laminate steel sheet It is known.

As conventional adhesives used when a polyvinyl chloride film is laminated on a steel sheet, for example, an epoxy resin, an amino resin adhesive, a polyester polyol and a polyisocyanate resin adhesive are known, and a single- There are two types of liquid type.

When these are used to laminate a polyvinyl chloride film on a steel sheet, necessary physical properties are generally achieved. However, since the polyolefin film is a hard-to-stick material, there is a problem that when the adhesive for a polyvinyl chloride film laminate is used as it is, defective adhesion is caused.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a lightweight composite steel sheet having excellent adhesion between a plastic layer and a steel sheet, and a method of manufacturing the same.

According to an embodiment of the present invention, And a polyamide resin layer formed on one side or both sides of the steel sheet, wherein the polyamide resin layer has 10 or more methylene groups in the repeating unit and the repeating unit is composed of all trans conformation A composite steel sheet excellent in adhesion can be provided.

The polyamide resin layer may include at least one selected from polyamide 10,12 and polyamide 11.

The surface energy of the polyamide resin layer may be 26 to 40 mN / m.

The thickness of the polyamide resin layer may be from 0.20 to 1.2 mm.

The thickness of the steel sheet may be 0.15 to 0.8 mm.

According to another embodiment of the present invention, there is provided a method of manufacturing a steel plate, And a step of laminating a polyamide resin layer on one side or both sides of the steel sheet and thermocompression bonding the same, wherein the polyamide resin layer has 10 or more methylene groups in the repeating unit, the repeating unit has an all trans conformation, A method for producing a composite steel sheet excellent in adhesion is provided.

The thermocompression bonding can be performed at 200 to 280 ° C.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a lightweight composite steel sheet which is excellent in adhesion with the steel sheet itself without using a separate adhesive layer.

Fig. 1 shows X-ray diffraction (XRD) analysis results of polyamide 11. Fig.
Fig. 2 shows X-ray diffraction (XRD) analysis results of polyamide 12. Fig.
Fig. 3 shows the results of observing the cross section of Example 1 with a Scanning Electron Microscope (SEM). Fig.
Fig. 4 shows the adhesive strength between the steel sheet and the plastic layer of the composite steel sheet according to the present invention.
Figure 5 shows the correlation between surface energy and adhesive strength.

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.

According to an embodiment of the present invention, And a polyamide resin layer formed on one side or both sides of the steel sheet, wherein the polyamide resin layer has 10 or more methylene groups in the repeating unit and the repeating unit is composed of all trans conformation A composite steel sheet excellent in adhesion can be provided.

A laminate steel sheet including a core material having a low specific gravity such as a plastic material between soft steel sheets can minimize the thickness of the soft steel sheet as compared with the core material and achieve weight reduction.

In addition, since the thickness of the entire laminated steel sheet including the core material increases, it is advantageous in that it can maintain rigidity and is used as an automotive outer plate material such as a hood or a door.

However, in the laminated steel sheet which has been studied so far, the thickness of the core material is thicker than the thickness of the outer sheet (soft steel sheet), and when the core material is combined with the outer sheet, its thickness increases largely, The effect can not be obtained.

Usually, a lightweight laminate steel sheet for automobiles is manufactured by placing a thin plate steel plate having a thickness of 0.2 to 0.3 mm on both sides, and a plastic core of polypropylene and polyamides disposed therebetween. The adhesion between the plastic core and the steel sheet is sufficient It is generally not possible to use a separate adhesive layer.

However, when an adhesive is applied, there is a problem that the time and cost of the additional process increase, and the heat resistance and the adhesive force during processing and after processing are reduced.

When a thermocompression process using a press is performed, resin or an adhesive at both ends is pushed out from the width of the metal plate. The resin or adhesive thus pushed out becomes a pollution factor in the laminating process, which causes a problem that the workability is lowered and the cost is increased.

Accordingly, the present inventors have repeatedly studied various materials. As a result, they found a polyamide resin layer capable of simultaneously achieving adhesion and light weight by improving the plastic layer of a laminated steel sheet, and completed the present invention.

The steel sheet which can be used in the present invention is not particularly limited, and examples thereof include stainless steel, aluminum, copper, zinc plating, metal plate, cold-rolled metal plate, colored metal plate and pickled metal plate.

On the other hand, the thickness of the steel sheet is preferably 0.15 to 0.8 mm. When the thickness of the steel sheet is less than 0.15 mm, it is difficult to secure the rigidity of the steel sheet, and rolling is difficult. On the other hand, when it exceeds 0.8 mm, there is a problem that weight reduction can not be achieved.

In the present invention, a polyamide resin layer formed on one side or both sides of the steel sheet without a separate adhesive layer is characterized in that the polyamide resin layer has 10 or more methylene groups in the repeating unit and the repeating units are all trans conformation consist of.

As the polyamide resin layer, it is preferable to use at least one selected from polyamide 10,12 and polyamide 11, and it is particularly preferable to use polyamide 10,12.

The structures of polyamide 10,12 and polyamide 11 are shown in Table 1 below. The structures of polyamide 6 and polyamide 12 are shown in Table 2 below.

폴리아미드-10,12

Polyamide-10,12

Polyamide-11

폴리아미드-6

Polyamide-6

Polyamide-10

As can be seen from the above Table 1, it can be seen that polyamide 10,12 and polyamide 11 contain at least 10 methylene groups in the repeating unit. Referring to Table 2, the polyamide 12 contains 11 methylene groups in the repeating unit, while the polyamide 6 contains 5 methylene groups.

The more the methylene group is contained in the polyamide repeating unit, the more excellent the flexibility and the adhesion, and the better the bending adhesion can be obtained. In the present invention, the use of the polyamide 10, 12 and the polyamide 11 having 10 or more methylene groups in the repeating unit as a resin layer formed on one side or both sides of the steel sheet can improve the adhesion to the steel sheet.

Further, the polyamide plastic layer of the present invention has a repeating unit of all trans conformation.

Figure 1 shows the XRD pattern of the polyamide 11 of the invention and Figure 2 shows the XRD pattern of the polyamide 12. As a result, it can be seen that the crystallization starts immediately at 180 ° C. in the cooling step, whereas the crystallization starts at about 170 ° C. in the case of the polyamide 12. This indicates that the crystallization starts with the all trans conformation and the twisted arrangement gauche conformation).

Specifically, as the temperature increases, the polyamide exhibits intergranular phase transition phenomenon known as Brill transition. This transition occurs reversibly even in the course of decreasing temperature. The temperature at which the brill transition occurs is strongly dependent on the crystallization temperature, and this dependence is due to differences in crystal completeness and crystal size.

The composite steel sheet according to the present invention can be produced by thermocompression, wherein the polyamide 10,12 and polyamide 11 having a trans arrangement (all trans conformation) are similar in temperature to the temperature at which the brill transition takes place, , The polyamide 12 forming the gauche conformation is different from the temperature at which the brill transition takes place and the temperature of the bonding process, so that the degree of the disorder of the methylene group becomes greater and the hydrogen bonding force is decreased.

The reduction of the hydrogen bonding force results in a decrease in adhesion with the steel sheet, which is not suitable for the use of the adhesive layer. The polyamide 12 contains 11 methylene groups in the repeating unit, but the adhesive strength is significantly lower than that when the polyamide 10, 12 and polyamide 11 are used.

Accordingly, it can be confirmed that the polyamide resin layer has ten or more methylene groups in the repeating unit, and that the repeating units are formed of all trans conformation, thereby improving the adhesion.

On the other hand, the polyamide resin layer of the present invention may have a surface energy of 26 to 40 mN / m. Adhesion is influenced by the intermolecular attraction between the different materials, and the attraction between the materials is determined by the surface energy. As the surface energy increases, the attraction increases. As the surface energy decreases, the attractive force between the molecules decreases.

Surface energy is known to be influenced by crystal faces, surface morphologies, surface states, and crystal structures of adjacent materials. As described above, the polyamide resin layer included in the present invention has a structure of all trans conformation.

The polyamide having the above-mentioned all-trans conformation has an increased surface energy due to the structural difference with the polyamide having the gauche conformation, and consequently the adhesion with the steel sheet can be increased .

The thickness of the plastic resin layer is preferably 0.20 to 1.2 mm. When the thickness of the plastic layer is less than 0.20 mm, it is difficult to secure the rigidity. On the other hand, when the thickness exceeds 1.2 mm, the lightening effect can not be achieved.

The composite steel sheet of the present invention comprises the steps of: preparing a steel sheet; And laminating the above-mentioned polyamide resin layer on one side or both sides of the steel sheet, followed by thermocompression bonding.

The manner of applying heat and pressure is not particularly limited, but according to one embodiment of the present invention, heat and pressure can be imparted by a heated press roll. In this case, a pneumatic cylinder, a hydraulic cylinder, an electric motor, or the like can be used as an actuator device for applying pressure to the press roll.

The thermocompression bonding is preferably performed at 200 to 280 ° C. If the thermocompression temperature is less than 200 ° C, the steel sheet and the plastic layer may not be adhered to each other. On the other hand, if the temperature exceeds 280 ° C, deterioration of the plastic may occur.

Hereinafter, the present invention will be described more specifically by way of specific examples. The following examples are provided to aid understanding of the present invention, and the scope of the present invention is not limited thereto.

Example

Example 1

The galvanized steel sheet was carried in a 99.5% acetone solution at room temperature for 4 minutes. Then, it was washed with distilled water, rubbed with a wiper or the like, and then dried to prepare a steel sheet.

The polyamide 11 was placed on the steel sheet, and then thermocompression was performed by a press to produce a composite steel sheet. At this time, the applied temperature is 230 ℃, pressure was 200kgf / cm ^2.

SEM photographs of cross sections of the obtained composite steel sheets were obtained and the results are shown in FIG.

Example 2

A composite steel sheet was prepared in the same manner as in Example 1, except that polyamide 10,12 was used instead of polyamide 11.

Comparative Example 1

A composite metal sheet was prepared in the same manner as in Example 1, except that polyamide 6 was used instead of polyamide 11.

Comparative Example 2

A composite metal sheet was prepared in the same manner as in Example 1, except that polyamide 6.6 was used instead of polyamide 11.

Comparative Example 3

A composite metal sheet was prepared in the same manner as in Example 1, except that polyamide 6.6 was used instead of polyamide 11.

Comparative Example 4

A composite metal plate was prepared in the same manner as in Example 1 except that glass fiber reinforced polyamide was used instead of polyamide 11.

Comparative Example 5

A composite metal sheet was prepared in the same manner as in Example 1 except that polyamide 12 was used instead of polyamide 11.

The adhesive strength and surface energy of the steel sheet and the plastic layer of the composite steel sheet thus prepared were measured and the X-ray diffraction patterns of the polyamide 11 and the polyamide 12 were compared to compare the X- Respectively.

Adhesive strength measurement of composite steel sheet

The adhesive strength between the steel sheet and the plastic layer of the composite steel sheet prepared according to the above Examples and Comparative Examples was measured and shown in FIG. 4, it can be seen that the composite steel sheet using the polyamide 11 and the polyamides 10 and 12 according to the present invention exhibits excellent adhesion.

Surface energy measurement

5 shows the results of observing the correlation between the surface energy (red) and the adhesive strength (black) of the composite metal sheets of Examples 1, 2, Comparative Examples 1 to 3 and Comparative Example 5 of the present invention. Referring to FIG. 5, it can be seen that the surface energies of the polyamide 11 and the polyamides 10 and 12 are large.

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 (7)

Steel plate; And
And a polyamide resin layer formed on one or both surfaces of the steel sheet,
Wherein the polyamide resin layer has 10 or more methylene groups in the repeating unit,
Wherein the repeating unit comprises polyamide (10,12) having a trans arrangement (all trans conformation).
delete The method according to claim 1,
Wherein the polyamide resin layer has a surface energy of 26 to 40 mN / m.
The method according to claim 1,
Wherein the thickness of the polyamide resin layer is 0.20 to 1.2 mm.
The method according to claim 1,
Wherein the steel sheet has a thickness of 0.15 to 0.8 mm.
Preparing a steel sheet; And
Laminating a polyamide resin layer on one side or both sides of the steel sheet and thermally bonding the same,
Wherein the polyamide resin layer comprises 10 or more methylene groups in the repeating unit and the repeating units are composed of all trans conformation of polyamide 10,12.
The method according to claim 6,
Wherein the hot pressing is performed at 200 to 280 ° C.

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