JPH11291399A - Polyester resin laminated steel sheet excellent in heat resistance for metal container, its manufacture and manufacture of metal container excellent in corrosion resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a low-cost polyester resin laminated steel sheet excellent in heat resistance for a can such as a 18-liter can, pail can or the like, wherein painting and printing are applied on an outer surface before can manufacturing and processing, and a manufacturing method thereof, and a manufacturing method of a metal container such as the 18-liter can, pail can or the like made of the polyester resin laminated steel sheet. SOLUTION: A laminated steel sheet has a polyester resin coat of two-layered structure. A top layer thereof has an orientated crystal structure. A lower layer thereof contacting with the steel sheet has 0.5-5 μm thickness and a melting starting temperature (Tms1) is 160 deg.C or higher, and a relation between a melting point (Tm1) of the lower layer and a melting point (Tm2) of the top layer is Tm1<=Tm2-10 deg.C. A total thickness of the resin coat of the polyester resin laminated steel sheet is 12-65 μm. And in the manufacturing method, the laminated steel sheet is manufactured at a temperature from Tms1+20 deg.C to Tm2-10 deg.C by heat contact bonding using a polyester film, and a metal container excellent in corrosion resistance is manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester resin-laminated steel sheet for a can type in which the outer surface is coated and printed before the processing of a metal container, particularly an 18-liter can or a pail can, a method for producing the same, and a polyester. The present invention relates to a method for manufacturing a metal container using a resin-laminated steel sheet.

[0002]

2. Description of the Related Art Conventionally, 18-liter cans, pail cans, etc.
When filling relatively corrosive contents, a method of applying double or triple coating is used to secure the inner surface corrosion resistance. There was a problem of carbon dioxide emission due to burning.
Also, depending on the contents, there is a problem that even if a double or triple coating is performed, it cannot withstand long-term filling and storage. Such contents may be filled in an atron can having an inner bag, but the filling operation is complicated and costly.

To solve these problems, Japanese Patent Application Laid-Open No. 7-232
As proposed in Japanese Patent No. 731, a large square can covered with a biaxially stretched polyester film except for an electrode resistance seam weld has been proposed. It describes a method obtained by thermocompression bonding a biaxially stretched polyester film via a primer or an adhesive, or a method obtained by direct heat bonding without using a primer or an adhesive.

[0004] However, the method using a primer or an adhesive requires a step of applying the primer or the adhesive to a film or a steel plate, which increases the cost.
When laminating a single-layer biaxially stretched polyester film without applying a primer or an adhesive, it is very important to secure the adhesion to the steel sheet while ensuring an oriented crystal structure with excellent corrosion resistance. It is necessary to manufacture a laminated steel sheet while performing extremely strict temperature control using expensive equipment, so that cost reduction cannot be expected.

[0005] Also, Japanese Patent Application Laid-Open No.
A laminated steel sheet having a layer coating structure and a method for producing the same have been proposed. This proposal has an advantage that the temperature control of the production of the laminated steel sheet is easy and the production equipment can be reduced in cost. However, for application to 18-liter cans, pail cans, etc., high corrosion resistance is required only on the inner surface, and the outer surface is usually printed to display the brand name of the product, and at the same time, the coating used as the base Also, for economic reasons, steel plates with resin laminated only on one side corresponding to the inner surface are often used, and in the baking process after painting and printing before processing, film misalignment or wicket mark It turned out to be a problem. In addition, film misalignment also occurs during welding repair coating and baking of caulking filler in the can manufacturing process. The problem is to prevent film misalignment and wicket marks due to welding repair painting in the baking step after coating printing on the outer surface of the can and in the can making step and baking of the caulking filler.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polyester resin laminated steel sheet for metal containers such as 18-liter cans and pail cans which is low in cost and has excellent corrosion resistance to contents. Specifically, in a baking process after coating and printing before processing a polyester laminated steel sheet having a two-layer film structure, film displacement or wicket marks are prevented. The film displacement is a phenomenon in which only the inner upper layer film of the two-layer film contracts, which is a problem in corrosion resistance.
The wicket mark is a dent mark generated in an organic film that comes into contact with a transfer stand (wicket) in a furnace, and poses a problem in corrosion resistance.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and its gist is as follows: (1) a laminated steel sheet having a two-layer polyester resin film on at least one side of the steel sheet; Wherein the upper layer has an oriented crystal structure, and the lower layer in contact with the steel sheet has a thickness of 0.5 to 5 μm.
m, the melting onset temperature (Tms1) is 160 ° C. or higher, and the lower layer melting point (Tm1) and upper layer melting point (Tm2) are Tm1 ≦ Tm.
2 to 10 ° C, and the total thickness of the resin film is 12 to 6
A polyester resin laminated steel sheet having excellent heat resistance, characterized in that the thickness is 5 μm.

(2) The steel plate is made of Sn plating, Ni plating, N
i. The polyester resin laminated steel sheet having excellent heat resistance according to the above (1), which is a steel sheet having an Sn plating or a chemical conversion treatment on its surface, or a chemical conversion treatment steel sheet having a chromium / chromate film. (3) The lower layer in contact with the steel sheet has a thickness of 0.5 to 5 μm, a melting onset temperature (Tms1) of 160 ° C. or more, and a lower layer melting point (T
m1) and the upper layer melting point (Tm2) is Tm1 ≦ Tm2-10 ° C.
Tms1 + 2 using a biaxially stretched polyester film of a two-layer structure having a total thickness of 12 to 65 μm.
A method for producing a polyester resin laminated steel sheet having excellent heat resistance, comprising thermocompression bonding at a temperature of 0 ° C to Tm2 to 10 ° C.

(4) A steel plate having a two-layered polyester resin film on at least the steel plate surface corresponding to the inner surface of the can is made of a laminated steel plate, and the steel plate surface corresponding to the outer surface of the can body is painted or printed and baked. In the production of a metal container, the coating has an oriented crystal structure, the lower layer in contact with the steel sheet has a thickness of 0.5 to 5 μm, and the lower layer melting point (Tm1) is T
m2-10 ° C or less, and the total thickness of the resin film is 12-6.
5 μm, and the baking temperature of the outer surface for coating or printing and the baking temperature of welding repair coating and caulking filler in the can making process are not more than the melting start temperature (Tms1) of the lower layer resin. Excellent metal container manufacturing method.

Hereinafter, the present invention will be described in detail. It has been found that the points for preventing the above-mentioned film displacement and wicket mark can be achieved both by improving the material of the polyester resin laminated steel sheet as the material or by improving the baking or heating temperature in the can making process. First, the polyester resin laminated steel sheet of the present invention will be described. In the laminated steel sheet having the two-layer polyester resin film of the present invention, the upper layer has an oriented crystal structure, and the lower layer in contact with the steel sheet has a thickness of 0.5.
５5 μm, melting start temperature (Tms1) is 160 ° C. or more, and lower melting point (Tm1) and upper melting point (Tm2) are Tm
It has a relation of 1 ≦ Tm2-10 ° C. and has a resin film having a total thickness of 12 to 65 μm on at least one surface of the steel sheet. Regarding the total thickness of the resin film, 12
If it is less than μm, there is a problem in corrosion resistance. On the other hand, if it exceeds 65 μm, it is economically disadvantageous.
5 μm is desirable.

When the thickness of the lower layer is less than 0.5 μm, it is insufficient to secure the adhesion between the resin film and the steel sheet.
This is because if it is larger than that, the possibility of generating a wicket mark increases. Since the upper film has an oriented crystal structure,
It does not soften to near the melting point. However,
It is desirable that the lower layer resin has an amorphous structure which is advantageous for securing adhesion. The amorphous structure softens above the Tg temperature. The Tg point of polyester resin is generally 70 ° C.
Before and after, since it is lower than the baking temperature (160 ° C or higher) of the paint printing on the outer surface of ordinary 18-liter cans, pail cans, etc., if the lower layer is unnecessarily thick, the wicket mark will be obtained even if the upper layer has an oriented crystal structure. Is caused. Preferably, it is 1.5 to 4 μm.

The reason that the upper layer resin has an oriented crystal structure is to ensure corrosion resistance. The crystalline structure of the polyester resin is higher in density and lower in the permeability of the substance than the amorphous structure. The non-oriented crystal structure has lower mechanical strength than the oriented crystal structure. Therefore, the upper layer has an oriented crystal structure. The oriented crystal structure described in the present invention has a plane orientation coefficient of 0.02.
Refer to the above. The plane orientation coefficient can be determined by the method described below. First, only the steel sheet of the resin-laminated steel sheet is chemically melted, and only the resin film is peeled off. The longitudinal, lateral, and thickness directions of the peeled film are measured with an Abbe refractometer. Desired.

Plane orientation coefficient: (X + Y) / 2-Z X: vertical refractive index Y: horizontal refractive index Z: refractive index in thickness direction

The melting start temperature (Tms1) of the lower layer is 160
It is found that when the temperature is lower than ℃, the film is likely to be misaligned. It has been found that film shift occurs when shrinkage stress is generated in the upper oriented crystalline film by heating and the lower resin cannot keep the upper resin shrinkage. It has been found that it is effective to make the melting start temperature of the lower layer higher than the baking temperature of coating printing. Preferably, the temperature is 180 ° C. or higher. The lower layer melting point (Tm1) is defined as Tm1 ≦ Tm2-10
C is set for stable production of laminated steel sheets. If Tm1> Tm2-10 ° C., a laminated steel sheet having an oriented crystal in the upper layer and having a resin film ensuring sufficient adhesion to the steel sheet cannot be efficiently manufactured at low cost. Preferably, the upper layer has a melting point (Tm2) of 240 ° C. or higher.

The base steel sheet used in the present invention includes a steel sheet which has not been subjected to base treatment, Sn plating, Ni plating, N
It is preferable to use an i-plated Sn plating or a steel sheet whose surface has been subjected to a chemical conversion treatment, or a chemical conversion treated steel sheet having a chromium / chromate film. Incidentally, the above-mentioned chemical conversion treatment generally refers to a chromate treatment, a phosphate treatment or the like applied to tinplate. The melting point and melting start temperature described in the present invention can be determined by measuring with a differential scanning calorimeter (DSC) at a heating rate of 10 ° C./min. The melting point is determined as the temperature at the top of the crystal melting peak, and the melting start temperature is determined as the temperature at which the crystal melting peak rises from the baseline.

The polyester resin used in the present invention is a saturated polyester resin and is a linear thermoplastic polyester obtained by polycondensation of a dicarboxylic acid and a diol, and is represented by polyethylene terephthalate. As the dicarboxylic acid component, terephthalic acid, isophthalic acid,
Phthalic acid, adipic acid, sebacic acid, azelaic acid,
2,6-naphthalenedicarboxylic acid, decanedicarboxylic acid, dodecanedicarboxylic acid, cyclohexanedicarboxylic acid or the like alone or as a mixture, and as the diol component, ethylene glycol, butanediol, decanediol, hexanediol, cyclohexanediol, neopentyl glycol Etc. alone or as a mixture. It may be a copolymer of two or more dicarboxylic acid components or diol components, or a copolymer with another monomer or polymer such as diethylene glycol or triethylene glycol.

Next, a method for producing the polyester resin laminated steel sheet of the present invention will be described. The lower layer in contact with the steel sheet has a thickness of 0.5 to 5 μm and a melting onset temperature (Tms1) of 16
0 ° C. or higher, and the lower layer melting point (Tm1) and upper layer melting point (Tm1)
2) has a relationship of Tm1 ≦ Tm2-10 ° C., and uses a biaxially stretched polyester film having a total thickness of 12 to 65 μm and a thermocompression bonding at a temperature of Tms1 + 20 ° C. to Tm2-10 ° C. A biaxially stretched polyester film having a two-layer structure can be prepared by extruding two kinds of resins together and stretching them in the longitudinal and transverse directions. For this reason, it can be produced very efficiently. This biaxially stretched polyester film having a two-layer structure is preliminarily subjected to Tms1 + 20 ° C.
Thermocompression bonding is possible by crimping a steel plate heated to a temperature of Tm2-10 ° C.

If the thermocompression bonding temperature is lower than Tms1 + 20 ° C., sufficient adhesion between the lower layer resin and the steel sheet cannot be ensured. If the temperature exceeds Tm2-10 ° C., the oriented crystal is broken, causing problems in corrosion resistance and mechanical strength. That's why. After the thermocompression bonding, it is desirable to rapidly cool down and to make the lower resin melted by the thermocompression bonding to have an amorphous structure. Further, after the thermocompression bonding, there is no problem in performing a slight retention within the range from the lower layer resin crystallization temperature to the upper layer melting point.

Next, a method for producing the metal container made of a polyester resin-laminated steel sheet of the present invention will be described. The production method of the present invention is to produce a laminated steel sheet having a two-layer polyester resin film on at least the steel sheet surface corresponding to the inner surface of the can, and then apply or print and bake the steel plate surface corresponding to the outer surface of the can body. In the manufacture of a metal container for can processing, the coating has an oriented crystal structure, the lower layer in contact with the steel sheet has a thickness of 0.5 to 5 μm, and the lower layer melting point (Tm1) is Tm.
2-10 ° C or less, and the total thickness of the resin film is 12-65.
μm, and the baking temperature of the outer surface for coating or printing and the baking temperature of the welding repair coating and caulking filler in the can-making process are not more than the melting start temperature (Tms1) of the lower layer resin.

It has been found that the upper limit of the baking temperature after coating printing on the outer surface of the can and the heating temperature in the can-making process can be prevented by setting the upper limit to the melting start temperature (Tms1) of the lower layer or lower. It has been found that film shift occurs when shrinkage stress is generated in the upper oriented crystalline film by heating and the lower resin cannot keep the upper resin shrinkage. Also, in the case of a can body in which the can body is formed by an electric seam welding method, a resin-laminated steel sheet having a portion that is not previously coated with a resin is used as in the case of normal coating,
After welding, it is desirable to perform repair painting with a polyester powder paint.

In the case where the can body is formed by caulking, it is desirable to fill the caulking section with an acrylic emulsion or urethane-based filler. Similarly, in the caulked portion between the main plate and the can body and the top plate and the can body,
It is desirable to fill similar fillers. Further, when the ring for attaching the ring is attached to the top plate by electric resistance welding, it is preferable to perform the repair painting with a polyester powder paint or a liquid paint substituted for an epoxy paint.

[0022]

EXAMPLES Examples of the present invention will be described together with comparative examples. Table 1 shows the used base steel sheets. First, Table 2 shows films used in Examples and Comparative Examples of the polyester resin laminated steel sheet of the present invention and the method for producing the same. Table 3 shows examples and comparative examples of the polyester resin laminated steel sheet of the present invention and the method for producing the same. The resin film shown in Table 2 is thermocompression-bonded to one side of the base steel sheet shown in Table 1, and the outer surface of the can body, which is not laminated, is painted or printed and baked, and the presence or absence of wicket marks and film displacement investigated. Further, an 18-liter can or a pail can was made in a can body, and the corrosion resistance was evaluated. The baking temperature of paint printing is 1
At 60 ° C for 20 minutes and at 180 ° C for 20 minutes, the corrosion resistance was evaluated by filling with Lion's liquid detergent lipon,
The state of corrosion was observed and evaluated at room temperature for one month.

Table 4 shows examples and comparative examples of the method for producing a metal container having excellent corrosion resistance according to the present invention.
After coating or printing and baking on the outer surface of the can of the laminated steel sheet of the material, the can was processed, filled with Lion's liquid detergent lipon, and observed for corrosion at room temperature for one month to evaluate the corrosion resistance. . The heating conditions of the can making method in Table 4 are the high-temperature conditions for the baking temperature of the repair coating of the welded portion and the baking temperature of the filler at the caulking portion. In the case of an 18-liter can, the body of the can was subjected to the electric seam welding method and the caulking method, the pail can was subjected to the electric seam welding method of the can body, and the electric seam weld was subjected to correction coating with a polyester powder paint. .
The caulked portion between the can body and the top plate and the caulked portion in the caulking method were filled with a urethane-based filler.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

[Table 3]

[0027]

[Table 4]

[0028]

As described above, the resin-laminated steel sheet of the present invention has excellent heat resistance,
Normal coating and printing can be performed using normal paints and inks used in 18-liter cans and pail cans without any problem of film displacement. For this reason, it is a steel plate for cans having excellent content resistance at low cost. Further, it is possible to use the resin film of the present invention on both surfaces of a steel plate and print only on the outer surface corresponding to the can and use it without any problem. Further, according to the production method of the present invention, it is possible to efficiently produce with low-cost equipment, and to provide a polyester resin laminated steel sheet which is low in cost and excellent in heat resistance. Further, according to the method for manufacturing a metal container of the present invention, it is possible to efficiently manufacture a low-cost metal container such as an 18-liter can or a pail without problems of wicket marks and film misalignment.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI C23C 28/00 C23C 28/00 C C25D 5/26 C25D 5/26 B

Claims (4)

[Claims] 1. A laminated steel sheet having a two-layered polyester resin film on at least one side of a steel sheet, wherein the upper layer has an oriented crystal structure and the lower layer in contact with the steel sheet has a thickness of 0.1 mm.
5-5 μm, melting start temperature (Tms1) is 160 ° C. or more, and lower melting point (Tm1) and upper melting point (Tm2) are Tm.
A polyester resin laminated steel sheet excellent in heat resistance, wherein 1 ≦ Tm2−10 ° C. and the total thickness of the resin film is 12 to 65 μm. 2. The heat-resistant steel sheet according to claim 1, wherein the steel sheet is a steel sheet having Sn plating, Ni plating, Sn plating under Ni or a chemical conversion treatment on the surface thereof, or a chemical conversion treated steel sheet having a chromium-chromate film. Polyester resin laminated steel sheet. 3. The lower layer in contact with the steel sheet has a thickness of 0.5 to 5 μm.
And the melting start temperature (Tms1) is 160 ° C. or higher, and the lower melting point (Tm1) and the upper melting point (Tm2) are Tm1 ≦ Tm2.
Tm using a biaxially stretched polyester film having a relationship of −10 ° C. and a total thickness of 12 to 65 μm and having a two-layer structure.
A method for producing a polyester resin laminated steel sheet having excellent heat resistance, wherein thermocompression bonding is performed at a temperature of s1 + 20 ° C to Tm2-10 ° C. 4. A steel plate having a two-layered polyester resin film on at least the steel plate surface corresponding to the inner surface of the can is used as a raw material, and the steel plate surface corresponding to the outer surface of the can body is painted or printed and baked. In the production of a metal container, the coating has an oriented crystal structure, the lower layer in contact with the steel sheet has a thickness of 0.5 to 5 μm, and the lower layer has a melting point (Tm1) of Tm2.
−10 ° C. or less, and the total thickness of the resin film is 12 to 65 μ
m, and the baking temperature of the outer surface for coating or printing and the baking temperature of the welding repair coating and caulking filler in the can-making process are lower than the melting start temperature (Tms1) of the lower resin. Excellent metal container manufacturing method.