JPH0376830B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is directed to chin-free steel (hereinafter referred to as TFS).
The present invention relates to a resin-laminated steel sheet laminated with a biaxially oriented polyester film, and particularly to a resin-laminated steel sheet suitable for use as a material for food cans. [Prior Art] Can materials for use in food cans have existed for a long time, but various studies are being conducted to further ensure long-term shelf life. For example, existing cans coated with TFS in combination with epoxy phenol paints may not have sufficient rust prevention ability, and many efforts are being made to develop materials for food cans that have higher rust prevention ability. As an example of this development activity, we have developed a product in which polyolefin film is laminated onto a metal plate (Japanese Patent Application Laid-open No.
141786), a copolymerized polyester resin film laminated on a metal plate (Japanese Patent Publication No. 57-23584), or a polyester film laminated on a metal plate with an adhesive (Japanese Patent Publication No. 58-39448, Japanese Patent Publication No. 58-39448) 61-20736). [Problems to be Solved by the Invention] Among the above-mentioned materials, for example, polyolefin films (polyethylene, polypropylene, etc.) that are laminated with metal plates have problems such as pressurization and sterilization. It does not have enough heat resistance to withstand the retort sterilization process,
In particular, when polyethylene film is used, even if it is modified, it cannot inherently exhibit satisfactory retortability, and in any case, the corrosion resistance of the can material after subsequent processing is poor. However, there is a problem in that it is difficult to be completely satisfactory. In addition, can stock formed by laminating the other copolymerized polyester resin film inevitably tends to be expensive, and has another problem in that it cannot be used economically for general can stock. are doing. Various research and trial-and-error efforts have been made to utilize it in a wide range of fields, not just can stock.
There is polyester film, and the use of this polyester film for can stock is of course a subject of consideration. Specifically, it is intended to use a polyester film laminated to a metal plate using an adhesive. Adhesives that are relatively frequently used at this time include, for example, polyester/urethane adhesives and saturated polyester adhesives (Japanese Patent Application Laid-open No. 10451/1983).
Alternatively, there is an epoxy type (Japanese Unexamined Patent Publication No. 61-20736, supra). An example of using a polyester/urethane adhesive is to laminate aluminum foil and polyester film and use this in light packaging, and there are many examples of such applications. However, in order to sufficiently bond the polyester film and metal plate, at least approximately
There are drawbacks such as the need for aging treatment at 40°C for 2 to 3 days, the use of organic solvents and the need for separate equipment for solvent recovery, and the need for large-scale equipment. Furthermore, since the method using an epoxy adhesive also uses a solvent, it has the disadvantage of requiring a large-scale device as in the previous case. In addition, products using saturated polyester adhesives have drawbacks such as the fact that the adhesive itself is a compound material containing multiple components, which requires time and effort for compounding, and the adhesive itself is expensive. In addition, attempts have been made to bond a polyester film to a metal plate by setting heat treatment conditions to specific conditions. In other words, a biaxially stretched polyethylene terephthalate (hereinafter referred to as O-PET) film is
When laminating to TES, TFS is heated to a temperature higher than the melting temperature of O-PET film (250℃ or higher)
The film is cooled immediately after lamination, and O
- Although the stress due to biaxial stretching on the adhesive surface of PET and TFS is relaxed, it still remains on the surface layer, making it possible to obtain a polyester film laminated steel sheet with good rust prevention properties. . However, in this case as well, if the cooling is too fast, good adhesion cannot be obtained, and if the cooling is too slow,
The disadvantageous result is that all the stresses due to stretching are relaxed. Moreover, the O-PET film itself cannot be used in a very thin film, and as a result, it is not possible to obtain a film that is satisfactory in terms of price. If we take these facts together and state the problems in the conventional technology conclusively, we will find that (1) the provision of a material that exhibits good rust prevention properties, and (2) the problem of making manufacturing equipment more compact, including the problem of making it easier to use. It was desired to solve the following problems: (3) establishment of manufacturing technology, and (3) supply of inexpensive products. [Means for Solving the Problems] As a result of various studies on the above-mentioned themes that need to be solved, this invention was developed by applying a modified polypropylene (modified PP) hot melt to one side of chin-free steel (TFS). via adhesive,
They achieved a resin-laminated steel sheet made by laminating a modified polyester film. [Structure and operation of the invention] The resin-laminated steel sheet constructed according to the present invention exhibits the desired effects only when the following individual requirements are satisfied. (1) Rust prevention In order to improve the rust prevention and fully demonstrate its effect, we use a modified polyester film with surface modification on the adhesive surface of the base TFS as a modified polypropylene hot melt. Lamination via mold adhesive is necessary. (2) Simplicity of manufacturing technology By using hot-melt modified PP for the adhesive layer,
Since lamination can be performed simply by thermocompression bonding, there is no need to use a solvent, and hence no solvent recovery equipment is required. We also use modified PP to modify polyester film.
By using pre-laminated steel sheets, lamination can be accomplished through a simple process of preheating the steel plates, film lamination, annealing, and cooling. (3) Supply of inexpensive products PP itself, along with polyethylene, is widely used as a general-purpose plastic resin, and belongs to the group of the cheapest materials. The modified PP used in the present invention, for example, does not exhibit sufficient adhesion if it is simply modified with maleic anhydride, so by using a base polymer of PP itself copolymerized with an ethylene component, it is possible to It was discovered that sufficient adhesiveness could be developed. Generally, when bonding surface-modified O-PET and modified PP, ethylene vinyl acetate copolymer resin (EVA) is often used as a hot melt adhesive, but this material has a low melting temperature. When trying to use it as a material for cans,
It was confirmed that sufficient performance in retort resistance was not achieved. Similarly, modified PE can be expected to have some adhesion, but is unsatisfactory in terms of retort resistance. Modified PP that can be used in the present invention is
Prices vary depending on the type and degree of degeneration, but start at 600 yen.
It is inexpensive at 700 yen/Kg. Since O-PET only needs to be about 12 μm thick, it is possible to use a relatively inexpensive material, and at the same time, it is also possible to easily modify the surface, and the cost increase due to this modification can be avoided. This has the advantage that the overall cost does not increase significantly. (4) Surface modification of O-PET O-PET itself has essentially low adhesion with various resins, as is clear from the fact that it is also used in release films. Therefore, if you try to use it as is for this purpose, it will not show any adhesive properties. Therefore, in order to improve the paintability of O-PET, chemical treatment methods (chemical treatment, solvent treatment, primer or polymer coating, coupling agent treatment, surfactant treatment, surface grafting, colloid treatment, etc.) and physical Surface modification is carried out by conventional treatment methods (ultraviolet irradiation treatment, plasma contact treatment, corona discharge treatment, etc.). In the present invention, sufficient adhesion can be obtained by using O-PET whose surface has been modified according to one of these methods. [Embodiments of the Invention] The structure of the resin-laminated steel sheet according to the present invention is shown in the drawings, in which 1 indicates TFS, 2 indicates an adhesive layer made of modified PP, and 3 indicates a synthetic resin film layer made of O-PET. It is. Example 1 Surface-modified O-PET with modified PP (modified propylene/ethylene copolymer) adhesive layer on steel plate
(corona discharge treated and chemically treated) and O-PET without surface modification were laminated to TFS to prepare a test piece for testing, and the adhesion was measured as described below. The following commercially available materials were used. *Modified PP: 30μm thick, (Mitsubishi Yuka Modic P-
310K) *Surface modified O-PET: 12μm thick, (Unitika's
(using PTM treated material) 30μm thick, (Toray corona discharge processed material,
Wettability of 50dyn/cm or more) 30μm thickness, (Toray, untreated) *Steel plate: 0.23mm thickness, TFS

[Table] In terms of adhesion immediately after lamination, the PTM treated and corona discharge processed products achieved almost satisfactory results, but the untreated products had almost no adhesion and were found to be unsatisfactory. did it. Example 2 Using surface-modified O-PET, the adhesive layer was laminated to TFS as modified PP (modified propylene/ethylene copolymer, the present invention), modified PE, ethylene adhesive, and urethane adhesive. The performance was evaluated using the following evaluation method. Sample ◎Surface modified O-PET: 12μm thick, (manufactured by Unitika,
PTM treatment) ◎Adhesive layer modified PP: 30μm thick (Mitsubishi Yuka,
MoDICP-310H) Modified PE: 30μm thick (Mitsui Petrochemical, ADMER NF-
550) EVA type: 30 μm thick (manufactured by Nippon Unicar) Urethane type: 4 to 5 μm thick (manufactured by Toyo Ink, AD-
506S/AD-RT1) Evaluation method (1) Adhesion test...Checkered Erichsen (3mm),
The lid processed material was tested under the following conditions. A Water retort treatment (127℃) 10 minutes, 30 minutes B 1.5% saline, retort treatment (127℃) 10
minutes, 30 minutes (2) Sulfide blackening resistance test...Conducted on processed lid products. Lactic acid 1.0ml + 1% soda sulfide 72ml + water 900ml
ml, retort treatment (127℃) 60 minutes (3) Secondary corrosion resistance test...UCC test (cross cut, Erichsen 5mm) 1.5% salt solution + 1.5% citric acid, 38℃, 98Hr immersion (4) Workability test... ...Bending test 0T to 3T bend (immersed in copper sulfate solution) The results are summarized in the following table.

【table】

〔Effect of the invention〕

(1) Satisfies the characteristics as a good rust-proof food can material. (2) Simplicity of manufacturing technology Since hot melt adhesive is used, it can be manufactured simply by thermocompression bonding. Since no solvent is used, there is no need for a drying oven or solvent recovery equipment. (3) Supply of inexpensive products Cheap O-PET, modified PP
Products can be made by combining.

[Brief explanation of drawings]

The drawing is a partially cutaway perspective view illustrating a resin laminated steel plate formed according to the present invention. 1... Metal plate (TFS), 2... Adhesive layer, 3...
Synthetic resin film.

Claims (1)

[Claims] 1. In a resin-laminated steel plate formed by bonding a polyester film to one surface of chin-free steel via an adhesive, the polyester film is a surface-modified polyester film, and the adhesive is made by copolymerizing polypropylene with an ethylene component. A resin-laminated steel sheet characterized by being made of hot-melt modified polypropylene.