JP2003025450A - Method for manufacturing laminated steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for laminating a polyolefin film to the polyethylene terephthalate film of a steel sheet coated with the film, using a non- adhesive, and a laminated steel sheet manufactured by the method. SOLUTION: One of materials for a metal can is a steel sheet (hereafter called 'PET steel sheet') laminated with the polyethylene terephthalate (hereafter called 'PET') film. A linear low-density polyethylene (=linear low-density polyethylene, hereafter called 'L-LDPE') film can be laminated on the PET surface, using the non-adhesive by treating the PET surface of the PET steel sheet by flame under specific conditions. Thus the can manufacturing method using a thermal fusion-bonding process which is conventionally not appropriate for the PET laminated can(hereafter called 'PET can'), can be adopted by using a composite laminated material. Thus a high-performance laminated can with the barrier properties of contents which are conventionally a problem as far as the L-LDPE laminated can (hereafter called 'L-LDPE can') is concerned, is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a resin film-coated metal plate (laminated metal plate) and a product using the same, and more specifically to a steel plate laminated with a polyethylene terephthalate film (hereinafter referred to as PET steel plate). While not subjecting the polyethylene terephthalate film surface (hereinafter referred to as PET surface) (hereinafter referred to as PET surface) to flame treatment, a linear low density polyethylene (= linear low density polyethylene) film (hereinafter referred to as L-LDPE film) is not adhered. The present invention relates to a method of laminating with an agent and an inner surface laminating can using this material.

[0002]

2. Description of the Prior Art Laminated steel sheets used as materials for metal cans include PET, L-LDPE, polypropylene,
Resin films such as polyamides and composites of these films have been used.

Especially in the material for 18 liter cans,
PET film and L-LDPE film are generally used, but since both have different physical properties such as content resistance and melting point, the content to be filled and the can manufacturing equipment owned by each company (can manufacturing method) In both cases, the laminated steel sheets that can be used are limited.

Regarding the content resistance, the chemical resistance of the resin inherent to the content (acid resistance, alkali resistance, etc.) is the most important, but from the conventional data, the biggest cause of the content resistance trouble is the film. This is due to the barrier performance and the can-making method (with or without adhesive).

Regarding the barrier property of the film, PET is generally superior to L-LDPE, but in the can-making method, the PET using L-LDPE can uses an adhesive because it is a non-adhesive / heat-sealing method. It can be said that it is more reliable than a can.

In the heat fusion can making method, a steel sheet laminated with a heat-sealable thermoplastic resin such as L-LDPE is used to make a can, and then the joint between the nadir and the case and the side seam of the case are formed. This is a method of heat-sealing the contact surfaces of inner surface films with each other by partial heating / or whole heating of the can, which has been put to practical use in the past.

The adhesive can-making method literally uses an adhesive to make a can. At the material stage, the can-making adhesive is applied to the joints between the nadir and the body and the side seams of the body. This is a method in which baking and coating are performed, and then the joint portion is heated and then adhered by heating, which is the most commonly used together with the welding seam method.

These can manufacturing methods basically depend on the equipment owned by each company, but in the case of laminated cans, PET can be used.
Since the wetting index and the melting point of L and L-LDPE are different, the former is forced to make a can by using an adhesive, and the latter is forced to make a can by heat-sealing inner surface films. That is, since PET cans and L-LDPE cans are manufactured by different can manufacturing facilities, it is inevitable to specialize in manufacturing either one of the laminated cans in addition to having both these facilities.

As described above, the L-LDPE can and the PET can are properly used depending not only on the suitability of the contents of the film itself but also on the can manufacturing method of each company. It can be said that they are used properly depending on whether or not the agent is used.

[0010] As an example, the PET can has a barrier property of the resin itself to the contents having extremely high permeability such as a paint for protecting wood, but the adhesive used in the joint of the can. Accidents such as the agent being affected and leaking or the adhesive component being eluted into the contents caused no leakage or alteration of the contents in the L-LDPE cans, but the inner surface of the cans was discolored by the permeable substance. There are cases where problems such as rusting and spot rust occur.

As described above, both the PET can and the L-LDPE can have advantages and disadvantages. Therefore, the PET can and the L-LDPE can are characterized by a content barrier property and the L-LDPE can is heat-sealed at the time of can making. There was a need to develop a material for laminated cans that also has good heat-sealing properties.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a new material for a laminated can which inherits the advantages of each of PET can and L-LDPE can and complements the disadvantages.

[0013]

A laminated steel plate for a metal can is manufactured by adhering a resin film to a steel plate as a raw material. This technique is well known and commonly used. In 18-liter cans, PET film and L-LDPE film are generally used.
The use of an adhesive is regarded as a problem for T cans, and the permeability of the contents is regarded as a problem for L-LDPE cans. That is, the PET can is required to have the heat fusion property of the L-LDPE can.
-LDPE cans are required to have the barrier properties that PET cans have. INDUSTRIAL APPLICABILITY The present invention provides a laminated can having a high barrier property, which can be manufactured by a heat fusion method by laminating an L-LDPE film with an adhesive-free material while applying a flame treatment to the PET surface of a PET steel sheet. It is intended to obtain a new material for manufacturing, and to provide a high-performance laminated can using the same.

The present invention is characterized by adhering an L-LDPE film without using an adhesive while flame-treating the PET surface of a steel sheet laminated with a PET film. (Claim 1)

Lamination between the PET film and the L-LDPE film is generally carried out by a method of using an adhesive such as an anchor coating agent or another adhesive resin in the intermediate layer. In terms of conformability during processing and non-destructive strength of cans, the required interlaminar strength cannot be satisfied, and the use of adhesives is shunned from the viewpoint of environmental resistance and hygiene. Not suitable as a film.

Although it is generally impossible to melt-bond L-LDPE to the PET surface without using an adhesive, according to the results of the practice of the present invention, the burning temperature on the PET surface of the PET steel sheet is 1300 ° C, combustion gas: air = 1:
By applying a flame with a ratio of 11 at a speed of 30 m / min and immediately roll-pressing the L-LDPE film, it is possible to obtain a very strong adhesive strength.

This is an oxidation product of a large amount of OH groups on the PET surface due to the combination of radicals generated by decomposition of the surface of the PET resin and oxygen, and the OH groups and the surface of the L-LDPE resin. It is presumed that CO, COOH and the like serve as a binder to obtain high adhesive strength.

In this process, PET film and
Only the outermost surface of the L-LDPE film is 1300 ° C or higher,
In addition, it is necessary to perform heat denaturation at a speed of 30 m / min or less, but it is difficult to apply this method to ordinary lamination of films because it is necessary to maintain good resin properties.

In a PET steel sheet for 18 liter cans, when the PET surface is exposed to a flame of 1300 ° C. at 30 m / min, the temperature rise of the steel sheet itself is 150 ° C. to 200 ° C.
Since the temperature is controlled within the range of ° C, only the outermost surface of the PET film is thermally metamorphosed and combined with radical oxygen in the flame. That is, by preliminarily laminating the PET film on the steel plate, it is possible to generate a functional group on the surface without impairing the physical properties of the PET resin.

The L-LDPE film has a surface holding temperature (500 ° C. to 100 ° C.) of the PET surface when rolled.
At 0 ° C.), only the outermost surface is decomposed to form an oxide. That is, only the adhesive surface with PET is modified while maintaining the necessary heat sealing property during can making.

As described above, since the functional groups formed on both the PET surface and the L-LDPE surface have surface activity, PE
It becomes possible to laminate the L-LDPE film on the surface of the T steel plate.

It is known that the flame treatment produces a large amount of OH groups as compared with the corona treatment, which seems to affect the improvement of the adhesive strength.

Furthermore, since the flame treatment is more likely to produce irregularities on the film surface than the corona treatment, the molten L-LDP is
The anchoring effect in which E is pushed into the uneven portion by the press roll also greatly contributes to the improvement of the adhesive strength.

In the laminated steel sheet for an 18-liter can produced by this method, the thickness of the PET film is considered to be about 5 μm to 150 μm, but generally 12 μ to 38 μ is preferable.

The thickness of the L-LDPE film for adhering to the PET surface is considered to be about 15 μm to 150 μm, but it is more preferably 30 μm to 80 μm on the can, and the total thickness with the PET film is 20 μm to 10 μm.
The range of 0 μm is preferable.

FIG. 1 is a schematic view of an apparatus for laminating L-LDPE films while flame-treating the PET surface of a PET steel plate.

FIG. 2 is a cross-sectional view of an inner laminated can made by using a laminated steel sheet manufactured by the above-mentioned method as a material, where is a joint between the nadir and the body, and is a side seam portion of the body. is there.

[0028]

By using the above method, PET
It is possible to obtain a material for an inner laminated can, which has a barrier property peculiar to a steel plate and can be manufactured by a heat fusion method peculiar to an L-LDPE can.

That is, by using this material,
It is possible to obtain a laminated can having excellent content resistance and manufactured by an adhesiveless method.

This laminating method can be applied not only to materials for metal cans, but also to metal plates such as aluminum plates and stainless plates, and various materials such as tanks, electric insulating materials and building materials can be used. It can be applied to products.

On the film surface of the laminated metal plate,
As a method of laminating another film, PE
Application is possible other than the combination of T and L-LDPE.

[0032]

Examples (1) While moving a TFS (tin-free steel) having a thickness of 0.32 mm with a 25 μm-thick PET laminated on the surface at a speed of 30 m / min,
Combustion temperature 1300 ° C. on ET surface, combustion gas: air = 1:
Treated with flame at a ratio of 11 and immediately after the thickness 70
An L-LDPE / PET composite laminated steel sheet was produced by roll-pressing an L-LDPE film having a thickness of μm, and the interlaminar strength between the L-LDPE film and the PET film was measured. (2) Using the above materials, a laminated can was manufactured by a heat fusion method, and the heat-sealed state of the winding fastening portion between the nadir and the body and the side seam portion of the body was measured. (3) A similar laminated can was filled with the following contents a to d, and a PET can and an L-LDPE can were also filled with the same contents, and an accelerated test at 45 ° C./14 days was performed for comparative evaluation. I did. a content 1 acid b content 2 alkali c content 3 paint remover d content 4 vegetable oil

Evaluation (1) 10 mm width, 90 ° T peeling (our method) (2) 10 mm width, 180 ° tensilon tensile test (our method) (3) Visual observation

Results (1) Delamination strength 2.2 kg (suitable) (2) Cohesive failure of L-LDPE layer (suitable) (3)

[Brief description of drawings]

FIG. 1 L of the PET surface of the PET steel plate while flame-treating
-A schematic view of an apparatus for laminating LDPE films.

FIG. 2 is a cross-sectional view of an inner laminated can made from a laminated steel sheet manufactured by using the above method,
Is the joint between the nadir and the torso, and is the side seam of the torso.

[Explanation of symbols]

1 flame treatment device 2 Laminating roll 3 PET laminated steel plate 4 L-LDPE / PET composite laminated steel sheet 5 Can inner surface side a PET film (layer) b L-LDPE film layer c Heat fusion part

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) // B29K 23:00 B29K 23:00 67:00 67:00 705: 12 705: 12 B29L 7:00 B29L 7:00 9:00 9:00 F Term (Reference) 3E062 AA04 AC03 AC07 JA07 JB04 JC07 JD01 JD06 4F100 AB01B AK42A AK63C BA03 BA10B BA10C EC032 EJ121 EJ192 EJ681 GB16 GB23 4F211 A02 A02 TH06 TH21 TN25 TN31 TQ03

Claims (3)

[Claims] 1. A method of laminating a linear low density polyethylene (= linear low-density polyethylene) film on a polyethylene terephthalate film surface of a steel sheet laminated with a polyethylene terephthalate film, wherein the polyethylene terephthalate film surface is subjected to flame treatment. A method for producing a linear low-density polyethylene / polyethylene terephthalate composite laminated steel sheet, which comprises bonding a linear low-density polyethylene (= linear low-density polyethylene) film with no adhesive. 2. A laminated metal plate produced by the method of claim 1. 3. An inner laminated can using the metal plate according to claim 2 as a raw material.